Reference signal transmission techniques for random access messages

ABSTRACT

Methods, systems, and devices for wireless communications are described for a two-step random access channel (RACH) procedure in which uplink random access preamble and message transmission occasions may span multiple transmission slots. Reference signal resources for transmitting a reference signal with a first random access message of the two-step RACH procedure may include at least one symbol in each of the multiple transmission slots. The reference signal resources, reference signal sequence, or both, may be identified based on a particular uplink random access message transmission occasion, random access preamble transmission occasion, random access preamble sequence configuration, or any combinations thereof.

CROSS REFERENCE

The present Application for Patent claims the benefit of U.S.Provisional Patent Application No. 62/842,133 by LEI et al., entitled“REFERENCE SIGNAL TRANSMISSION TECHNIQUES FOR RANDOM ACCESS MESSAGES,”filed May 2, 2019, assigned to the assignee hereof, and expresslyincorporated herein.

BACKGROUND

The following relates generally to wireless communications, and morespecifically to reference signal transmission techniques for randomaccess messages.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal frequency division multiple access (OFDMA), or discreteFourier transform spread orthogonal frequency division multiplexing(DFT-S-OFDM).

A wireless multiple-access communications system may include a number ofbase stations or network access nodes, each simultaneously supportingcommunication for multiple communication devices, which may be otherwiseknown as user equipment (UE). When connecting to a base station toreceive and/or transmit communications, a UE may perform a random accesschannel (RACH) procedure to establish the connection with the basestation. Efficient techniques for determining configuration informationfor one or more messages of the RACH procedure may help to enhance theefficiency of a wireless communications system.

SUMMARY

The described techniques relate to improved methods, systems, devices,and apparatuses that support reference signal transmission techniquesfor random access messages. Various techniques described herein providefor a two-step random access channel (RACH) procedure in which RACHresources may span multiple transmission slots. In some cases, referencesignal resources for transmitting a reference signal with the firstrandom access message of the two-step RACH procedure may include atleast one symbol in each of the multiple transmission slots. In somecases, the reference signal resources within each of the multipletransmission slots may be identified based at least in part on aparticular uplink shared channel (e.g., a physical uplink shared channel(PUSCH)) transmission occasion (e.g., a PUSCH occasion (PO)) that isused to transmit the first random access message. In some cases, a basestation may provide system information that indicates two or moreavailable random access occasions and two or more available uplinkshared channel transmission occasions within each of the two or moreavailable random access occasions. In such cases, a UE may select arandom access occasion and an uplink shared channel transmissionoccasion and determine a reference signal sequence for a referencesignal to be transmitted with the first random access message based onidentifiers associated with the selected random access occasion and anuplink shared channel transmission occasion.

A method of wireless communication at a UE is described. The method mayinclude receiving system information from a base station, the systeminformation including an indication of two or more available uplinkshared channel transmission occasions for a random access messagetransmission from the UE, selecting a first uplink shared channeltransmission occasion of the two or more available uplink shared channeltransmission occasions for transmission of a first random accessmessage, where the first uplink shared channel transmission occasionspans at least two transmission slots, determining, based on the systeminformation, reference signal resources within the first uplink sharedchannel transmission occasion for transmitting a reference signal withthe first random access message, where the reference signal resourcesinclude at least one symbol in each of the two or more transmissionslots, formatting the first random access message based on the selectedfirst uplink shared channel transmission occasion and the determinedreference signal resources, the first random access message includingthe reference signal and uplink shared channel data, and transmittingthe first random access message to the base station.

An apparatus for wireless communication at a UE is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be executable by the processor to cause the apparatusto receive system information from a base station, the systeminformation including an indication of two or more available uplinkshared channel transmission occasions for a random access messagetransmission from the UE, select a first uplink shared channeltransmission occasion of the two or more available uplink shared channeltransmission occasions for transmission of a first random accessmessage, where the first uplink shared channel transmission occasionspans at least two transmission slots, determine, based on the systeminformation, reference signal resources within the first uplink sharedchannel transmission occasion for transmitting a reference signal withthe first random access message, where the reference signal resourcesinclude at least one symbol in each of the two or more transmissionslots, format the first random access message based on the selectedfirst uplink shared channel transmission occasion and the determinedreference signal resources, the first random access message includingthe reference signal and uplink shared channel data, and transmit thefirst random access message to the base station.

Another apparatus for wireless communication at a UE is described. Theapparatus may include means for receiving system information from a basestation, the system information including an indication of two or moreavailable uplink shared channel transmission occasions for a randomaccess message transmission from the UE, selecting a first uplink sharedchannel transmission occasion of the two or more available uplink sharedchannel transmission occasions for transmission of a first random accessmessage, where the first uplink shared channel transmission occasionspans at least two transmission slots, determining, based on the systeminformation, reference signal resources within the first uplink sharedchannel transmission occasion for transmitting a reference signal withthe first random access message, where the reference signal resourcesinclude at least one symbol in each of the two or more transmissionslots, formatting the first random access message based on the selectedfirst uplink shared channel transmission occasion and the determinedreference signal resources, the first random access message includingthe reference signal and uplink shared channel data, and transmittingthe first random access message to the base station.

A non-transitory computer-readable medium storing code for wirelesscommunication at a UE is described. The code may include instructionsexecutable by a processor to receive system information from a basestation, the system information including an indication of two or moreavailable uplink shared channel transmission occasions for a randomaccess message transmission from the UE, select a first uplink sharedchannel transmission occasion of the two or more available uplink sharedchannel transmission occasions for transmission of a first random accessmessage, where the first uplink shared channel transmission occasionspans at least two transmission slots, determine, based on the systeminformation, reference signal resources within the first uplink sharedchannel transmission occasion for transmitting a reference signal withthe first random access message, where the reference signal resourcesinclude at least one symbol in each of the two or more transmissionslots, format the first random access message based on the selectedfirst uplink shared channel transmission occasion and the determinedreference signal resources, the first random access message includingthe reference signal and uplink shared channel data, and transmit thefirst random access message to the base station.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a randomaccess preamble for transmission with the first random access message,and determining a reference signal sequence for the reference signalbased on the random access preamble. In some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein, the reference signal may be a demodulation reference signal, andwhere the reference signal resources in each of the two or moretransmission slots may be front-loaded in each of the at least twotransmission slots, may be distributed in each of the at least twotransmission slots, or combinations thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the formatting further mayinclude operations, features, means, or instructions for applying acover code to the reference signal that may be associated with the UE.In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the cover code may be abinary orthogonal cover code, a non-binary orthogonal cover code, or aquasi-orthogonal cover code. In some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein, the formatting further may include operations, features, means,or instructions for determining the cover code based on a codebookindicated by the system information, and where the cover code spans allof the reference signal resources in each of the two or moretransmission slots. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the formattingfurther may include operations, features, means, or instructions fordetermining separate cover codes associated with each of the two or moretransmission slots based on different codebooks associated with each ofthe two or more transmission slots. In some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein, the different codebooks may be each associated with differentsubsets of the two or more available uplink shared channel transmissionoccasions. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the cover codemay be applied separately or jointly across frequency domain resourcesassociated with the two or more available uplink shared channeltransmission occasions.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the UE is in a radio resourcecontrol (RRC) connected state and the system information is received viaRRC signaling.

A method of wireless communication at a UE is described. The method mayinclude receiving system information from a base station, the systeminformation including an indication of two or more available randomaccess occasions and two or more available uplink shared channeltransmission occasions within each of the two or more available randomaccess occasions, where each of the two or more available random accessoccasions is indicated by an associated random access occasionidentifier and each of the two or more available uplink shared channeltransmission occasions is indicated by an associated uplink sharedchannel transmission occasion identifier, selecting a first randomaccess occasion of the two or more available random access occasions anda first uplink shared channel transmission occasion of the two or moreavailable uplink shared channel transmission occasions for transmissionof a first random access message, determining, based on a first randomaccess occasion identifier associated with the first random accessoccasion, a first uplink shared channel transmission occasion identifierassociated with the first uplink shared channel transmission occasion,or combinations thereof, a reference signal sequence for a referencesignal to be transmitted with the first random access message, andtransmitting the first random access message to the base station.

An apparatus for wireless communication at a UE is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be executable by the processor to cause the apparatusto receive system information from a base station, the systeminformation including an indication of two or more available randomaccess occasions and two or more available uplink shared channeltransmission occasions within each of the two or more available randomaccess occasions, where each of the two or more available random accessoccasions is indicated by an associated random access occasionidentifier and each of the two or more available uplink shared channeltransmission occasions is indicated by an associated uplink sharedchannel transmission occasion identifier, select a first random accessoccasion of the two or more available random access occasions and afirst uplink shared channel transmission occasion of the two or moreavailable uplink shared channel transmission occasions for transmissionof a first random access message, determine, based on a first randomaccess occasion identifier associated with the first random accessoccasion, a first uplink shared channel transmission occasion identifierassociated with the first uplink shared channel transmission occasion,or combinations thereof, a reference signal sequence for a referencesignal to be transmitted with the first random access message, andtransmit the first random access message to the base station.

Another apparatus for wireless communication at a UE is described. Theapparatus may include means for receiving system information from a basestation, the system information including an indication of two or moreavailable random access occasions and two or more available uplinkshared channel transmission occasions within each of the two or moreavailable random access occasions, where each of the two or moreavailable random access occasions is indicated by an associated randomaccess occasion identifier and each of the two or more available uplinkshared channel transmission occasions is indicated by an associateduplink shared channel transmission occasion identifier, selecting afirst random access occasion of the two or more available random accessoccasions and a first uplink shared channel transmission occasion of thetwo or more available uplink shared channel transmission occasions fortransmission of a first random access message, determining, based on afirst random access occasion identifier associated with the first randomaccess occasion, a first uplink shared channel transmission occasionidentifier associated with the first uplink shared channel transmissionoccasion, or combinations thereof, a reference signal sequence for areference signal to be transmitted with the first random access message,and transmitting the first random access message to the base station.

A non-transitory computer-readable medium storing code for wirelesscommunication at a UE is described. The code may include instructionsexecutable by a processor to receive system information from a basestation, the system information including an indication of two or moreavailable random access occasions and two or more available uplinkshared channel transmission occasions within each of the two or moreavailable random access occasions, where each of the two or moreavailable random access occasions is indicated by an associated randomaccess occasion identifier and each of the two or more available uplinkshared channel transmission occasions is indicated by an associateduplink shared channel transmission occasion identifier, select a firstrandom access occasion of the two or more available random accessoccasions and a first uplink shared channel transmission occasion of thetwo or more available uplink shared channel transmission occasions fortransmission of a first random access message, determine, based on afirst random access occasion identifier associated with the first randomaccess occasion, a first uplink shared channel transmission occasionidentifier associated with the first uplink shared channel transmissionoccasion, or combinations thereof, a reference signal sequence for areference signal to be transmitted with the first random access message,and transmit the first random access message to the base station.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the determining the referencesignal sequence further may include operations, features, means, orinstructions for determining an initialization seed for a polynomialgenerator that generates the reference signal sequence, theinitialization seed based on one or more of the first uplink sharedchannel transmission occasion identifier, the first random accessoccasion identifier, a preamble sequence identifier provided in thesystem information, or any combinations thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the initialization seed maybe further based on one or more of a symbol index of a symbol within atransmission slot that carries the reference signal, a transmission slotnumber of the transmission slot within a radio frame, a sub-carrierspacing used for transmitting the first random access message, one ormore scaling constants, or any combinations thereof. In some examples ofthe method, apparatuses, and non-transitory computer-readable mediumdescribed herein, the polynomial generator may be a closed-formpolynomial generator that generates a pseudo-random noise (PN) sequence.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the reference signal sequencemay be a preconfigured gold sequence that may be selected from a set ofavailable preconfigured gold sequences based on the first random accessoccasion identifier and the first uplink shared channel transmissionoccasion identifier.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the reference signal sequenceincludes a cyclic prefix orthogonal frequency division multiplexing(CP-OFDM) waveform demodulation reference signal (DMRS) sequence. Insome examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the determining the referencesignal sequence further may include operations, features, means, orinstructions for determining a base sequence based on one or more of agroup index, a sequence index, a cyclic shift, or any combinationsthereof, indicated in the system information. In some examples of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, the group index may be determined based on one or moreof the first uplink shared channel transmission occasion identifier, thefirst random access occasion identifier, a preamble sequence identifierprovided in the system information, or any combinations thereof. In someexamples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the group index may befurther determined based on a group hopping index provided in the systeminformation, a reference signal sequence hopping index provided in thesystem information, or any combinations thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the base sequence may beselected from a set of available base sequences including Zadoff-Chusequences, computer generated sequences, modified chirp sequences,composite sequences with low peak to average power ratios, or anycombinations thereof. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the referencesignal sequence includes a discrete Fourier transform spread orthogonalfrequency division multiplexing (DF-s-OFDM) waveform demodulationreference signal (DMRS) sequence.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the two or more availablerandom access occasions and two or more available uplink shared channeltransmission occasions are associated with an RRC state. In someexamples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the first random accessoccasion and the first uplink shared channel transmission occasion maybe selected based at least in part on the UE being in the RRC state.

A method of wireless communication at a base station is described. Themethod may include determining two or more uplink shared channeltransmission occasions for a random access message transmission from atleast a first UE of a set of UEs served by the base station, where atleast a first uplink shared channel transmission occasion of the two ormore uplink shared channel transmission occasions spans two or moretransmission slots, configuring reference signal resources for each ofthe two or more uplink shared channel transmission occasions, where thereference signal resources for the first uplink shared channeltransmission occasion include at least one symbol in each of the two ormore transmission slots, transmitting system information to the set ofUEs that indicates the two or more uplink shared channel transmissionoccasions, and the configured reference signal resources, that areavailable for random access message transmissions of the set of UEs, andreceiving a first random access message from the first UE based on areference signal transmitted in the reference signal resourcesassociated with the uplink shared channel transmission occasion selectedby the first UE for transmission of the first random access message.

An apparatus for wireless communication at a base station is described.The apparatus may include a processor, memory in electroniccommunication with the processor, and instructions stored in the memory.The instructions may be executable by the processor to cause theapparatus to determine two or more uplink shared channel transmissionoccasions for a random access message transmission from at least a firstUE of a set of UEs served by the base station, where at least a firstuplink shared channel transmission occasion of the two or more uplinkshared channel transmission occasions spans two or more transmissionslots, configure reference signal resources for each of the two or moreuplink shared channel transmission occasions, where the reference signalresources for the first uplink shared channel transmission occasioninclude at least one symbol in each of the two or more transmissionslots, transmit system information to the set of UEs that indicates thetwo or more uplink shared channel transmission occasions, and theconfigured reference signal resources, that are available for randomaccess message transmissions of the set of UEs, and receive a firstrandom access message from the first UE based on a reference signaltransmitted in the reference signal resources associated with the uplinkshared channel transmission occasion selected by the first UE fortransmission of the first random access message.

Another apparatus for wireless communication at a base station isdescribed. The apparatus may include means for determining two or moreuplink shared channel transmission occasions for a random access messagetransmission from at least a first UE of a set of UEs served by the basestation, where at least a first uplink shared channel transmissionoccasion of the two or more uplink shared channel transmission occasionsspans two or more transmission slots, configuring reference signalresources for each of the two or more uplink shared channel transmissionoccasions, where the reference signal resources for the first uplinkshared channel transmission occasion include at least one symbol in eachof the two or more transmission slots, transmitting system informationto the set of UEs that indicates the two or more uplink shared channeltransmission occasions, and the configured reference signal resources,that are available for random access message transmissions of the set ofUEs, and receiving a first random access message from the first UE basedon a reference signal transmitted in the reference signal resourcesassociated with the uplink shared channel transmission occasion selectedby the first UE for transmission of the first random access message.

A non-transitory computer-readable medium storing code for wirelesscommunication at a base station is described. The code may includeinstructions executable by a processor to determine two or more uplinkshared channel transmission occasions for a random access messagetransmission from at least a first UE of a set of UEs served by the basestation, where at least a first uplink shared channel transmissionoccasion of the two or more uplink shared channel transmission occasionsspans two or more transmission slots, configure reference signalresources for each of the two or more uplink shared channel transmissionoccasions, where the reference signal resources for the first uplinkshared channel transmission occasion include at least one symbol in eachof the two or more transmission slots, transmit system information tothe set of UEs that indicates the two or more uplink shared channeltransmission occasions, and the configured reference signal resources,that are available for random access message transmissions of the set ofUEs, and receive a first random access message from the first UE basedon a reference signal transmitted in the reference signal resourcesassociated with the uplink shared channel transmission occasion selectedby the first UE for transmission of the first random access message.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a randomaccess preamble of the first random access message, determining areference signal sequence of the reference signal of the first randomaccess message based on the random access preamble of the first randomaccess message, and demodulating and decoding a payload of the firstrandom access message based on the random access preamble and thereference signal sequence. In some examples of the method, apparatuses,and non-transitory computer-readable medium described herein, thereference signal may be a demodulation reference signal, and where thereference signal resources in each of the two or more transmission slotsmay be front-loaded in each of the at least two transmission slots, maybe distributed in each of the at least two transmission slots, orcombinations thereof.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for decoding the firstrandom access message based on a cover code applied to the referencesignal that may be associated with the first UE. In some examples of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, the cover code may be a binary orthogonal cover code,a non-binary orthogonal cover code, or a quasi-orthogonal cover code. Insome examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the configuring further mayinclude operations, features, means, or instructions for configuring anindication of two or more cover code codebooks in the systeminformation, and where at least a first cover code of a first cover codecodebook spans all of the reference signal resources in each of the twoor more transmission slots of the first uplink shared channeltransmission occasion. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, theconfiguring further may include operations, features, means, orinstructions for configuring different cover code codebooks for each ofthe two or more transmission slots of the first uplink shared channeltransmission occasion. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the differentcover code codebooks may be each associated with different subsets ofthe two or more uplink shared channel transmission occasions. In someexamples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the cover codes may beapplied separately or jointly across frequency domain resourcesassociated with the two or more uplink shared channel transmissionoccasions.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the two or more uplink sharedchannel transmission occasions are determined for an RRC state.

A method of wireless communication at a base station is described. Themethod may include configuring two or more random access occasions andtwo or more uplink shared channel transmission occasions within each ofthe two or more random access occasions that are available for at leasta first UE to transmit a first random access message, where each of thetwo or more random access occasions has an associated random accessoccasion identifier and each of the two or more uplink shared channeltransmission occasions has an associated uplink shared channeltransmission occasion identifier, transmitting system information to aset of UEs, the system information including random access occasionidentifiers of the configured two or more random access occasions anduplink shared channel transmission occasion identifiers of theconfigured two or more uplink shared channel transmission occasions,receiving the first random access message from the first UE in a firstuplink shared channel transmission occasion of a first random accessoccasions, where the first random access message includes a referencesignal, identifying, based on a first random access occasion identifierassociated with the first random access occasion and a first uplinkshared channel transmission occasion identifier associated with thefirst uplink shared channel transmission occasion, a reference signalsequence for the reference signal transmitted with the first randomaccess message, and demodulating the first random access message basedon the determined reference signal sequence.

An apparatus for wireless communication at a base station is described.The apparatus may include a processor, memory in electroniccommunication with the processor, and instructions stored in the memory.The instructions may be executable by the processor to cause theapparatus to configure two or more random access occasions and two ormore uplink shared channel transmission occasions within each of the twoor more random access occasions that are available for at least a firstUE to transmit a first random access message, where each of the two ormore random access occasions has an associated random access occasionidentifier and each of the two or more uplink shared channeltransmission occasions has an associated uplink shared channeltransmission occasion identifier, transmit system information to a setof UEs, the system information including random access occasionidentifiers of the configured two or more random access occasions anduplink shared channel transmission occasion identifiers of theconfigured two or more uplink shared channel transmission occasions,receive the first random access message from the first UE in a firstuplink shared channel transmission occasion of a first random accessoccasions, where the first random access message includes a referencesignal, identify, based on a first random access occasion identifierassociated with the first random access occasion and a first uplinkshared channel transmission occasion identifier associated with thefirst uplink shared channel transmission occasion, a reference signalsequence for the reference signal transmitted with the first randomaccess message, and demodulate the first random access message based onthe determined reference signal sequence.

Another apparatus for wireless communication at a base station isdescribed. The apparatus may include means for configuring two or morerandom access occasions and two or more uplink shared channeltransmission occasions within each of the two or more random accessoccasions that are available for at least a first UE to transmit a firstrandom access message, where each of the two or more random accessoccasions has an associated random access occasion identifier and eachof the two or more uplink shared channel transmission occasions has anassociated uplink shared channel transmission occasion identifier,transmitting system information to a set of UEs, the system informationincluding random access occasion identifiers of the configured two ormore random access occasions and uplink shared channel transmissionoccasion identifiers of the configured two or more uplink shared channeltransmission occasions, receiving the first random access message fromthe first UE in a first uplink shared channel transmission occasion of afirst random access occasions, where the first random access messageincludes a reference signal, determining, based on a first random accessoccasion identifier associated with the first random access occasion anda first uplink shared channel transmission occasion identifierassociated with the first uplink shared channel transmission occasion, areference signal sequence for the reference signal transmitted with thefirst random access message, and demodulating the first random accessmessage based on the determined reference signal sequence.

A non-transitory computer-readable medium storing code for wirelesscommunication at a base station is described. The code may includeinstructions executable by a processor to configure two or more randomaccess occasions and two or more uplink shared channel transmissionoccasions within each of the two or more random access occasions thatare available for at least a first UE to transmit a first random accessmessage, where each of the two or more random access occasions has anassociated random access occasion identifier and each of the two or moreuplink shared channel transmission occasions has an associated uplinkshared channel transmission occasion identifier, transmit systeminformation to a set of UEs, the system information including randomaccess occasion identifiers of the configured two or more random accessoccasions and uplink shared channel transmission occasion identifiers ofthe configured two or more uplink shared channel transmission occasions,receive the first random access message from the first UE in a firstuplink shared channel transmission occasion of a first random accessoccasions, where the first random access message includes a referencesignal, determining, based on a first random access occasion identifierassociated with the first random access occasion and a first uplinkshared channel transmission occasion identifier associated with thefirst uplink shared channel transmission occasion, a reference signalsequence for the reference signal transmitted with the first randomaccess message, and demodulate the first random access message based onthe determined reference signal sequence.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the determining the referencesignal sequence further may include operations, features, means, orinstructions for determining an initialization seed for a polynomialgenerator that generates the reference signal sequence, theinitialization seed based on one or more of the first uplink sharedchannel transmission occasion identifier, the first random accessoccasion identifier, a preamble sequence identifier provided in thesystem information, or any combinations thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the initialization seed maybe further based on one or more of a symbol index of a symbol within atransmission slot that carries the reference signal, a transmission slotnumber of the transmission slot within a radio frame, a sub-carrierspacing used for transmitting the first random access message, one ormore scaling constants, or any combinations thereof. In some examples ofthe method, apparatuses, and non-transitory computer-readable mediumdescribed herein, the polynomial generator may be a closed-formpolynomial generator that generates a pseudo-random noise (PN) sequence.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the reference signal sequencemay be a preconfigured gold sequence that may be selected from a set ofavailable preconfigured gold sequences based on the first random accessoccasion identifier and the first uplink shared channel transmissionoccasion identifier.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the reference signal sequenceincludes a cyclic prefix orthogonal frequency division multiplexing(CP-OFDM) waveform demodulation reference signal (DMRS) sequence.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the determining the referencesignal sequence further may include operations, features, means, orinstructions for determining a base sequence based on one or more of agroup index, a sequence index, a cyclic shift, or any combinationsthereof, indicated in the system information. In some examples of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, the group index may be determined based on one or moreof the first uplink shared channel transmission occasion identifier, thefirst random access occasion identifier, a preamble sequence identifierprovided in the system information, or any combinations thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the group index may befurther determined based on a group hopping index provided in the systeminformation, a reference signal sequence hopping index provided in thesystem information, or any combinations thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the base sequence may beselected from a set of available base sequences including Zadoff-Chusequences, computer generated sequences, modified chirp sequences,composite sequences with low peak to average power ratios, or anycombinations thereof. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the referencesignal sequence includes a discrete Fourier transform spread orthogonalfrequency division multiplexing (DFT-s-OFDM) waveform demodulationreference signal (DMRS) sequence.

some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the system information istransmitted in a system information block (SIB), in an RRC message, orboth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communicationsthat supports reference signal transmission techniques for random accessmessages in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a portion of a wireless communicationsthat supports reference signal transmission techniques for random accessmessages in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a two-step random access channel (RACH)procedure that supports reference signal transmission techniques inaccordance with aspects of the present disclosure.

FIG. 4A illustrates an example of a channel structure that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure.

FIG. 4B illustrates an example of a transmit chain that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure.

FIG. 5 illustrates an example of a slot structure that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure.

FIG. 6 illustrates an example of a process flow that supports referencesignal transmission techniques for random access messages in accordancewith aspects of the present disclosure.

FIG. 7 illustrates an example of a process flow that supports referencesignal transmission techniques for random access messages in accordancewith aspects of the present disclosure.

FIGS. 8 and 9 show block diagrams of devices that support referencesignal transmission techniques for random access messages in accordancewith aspects of the present disclosure.

FIG. 10 shows a block diagram of a communications manager that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure.

FIG. 11 shows a diagram of a system including a device that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure.

FIGS. 12 and 13 show block diagrams of devices that support referencesignal transmission techniques for random access messages in accordancewith aspects of the present disclosure.

FIG. 14 shows a block diagram of a communications manager that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure.

FIG. 15 shows a diagram of a system including a device that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure.

FIGS. 16 through 21 show flowcharts illustrating methods that supportreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure.

DETAILED DESCRIPTION

In some network deployment scenarios, a base station and a userequipment (UE) may simultaneously use different random access proceduresto meet different requirements for the system. For example, thedifferent random access procedures may include two-step random accesschannel (RACH) procedures and four-step RACH procedures, and thedifferent requirements may include capacity limitations, latencyrequirements, reliability requirements, implementation complexityspecifications, and the like. In some cases, different physical uplinkshared channel (PUSCH) occasions (POs) may be defined that can be usedfor both or either of the RACH procedures. For example, the differentPOs may include one or more RACH occasions (ROs) that may be associatedwith a two-step or four-step RACH procedure. In some cases, a two-stepRACH procedure may use ROs separate from a four-step RACH procedure ormay share ROs with a four-step RACH procedure but use different sets ofpreamble sequences.

The two-step RACH procedure may include a first random access message(e.g., msgA) transmitted by a UE, which may include a RACH preamble anda payload, and a second random access message (e.g., msgB) transmittedby a base station in response to the first random access message. Insome cases, the UE may transmit the preamble and payload portions of thefirst random access message in same or different slots and in a samebandwidth, partially overlapping bandwidths, or disjoint bandwidthsbased on the configuration information. The base station may transmitthe configuration information in a system information (SI) transmissionor via radio resource control (RRC) signaling. For example, theconfiguration information may be included in a system information block(SIB) and/or an RRC message.

In some cases, a UE's reception of configuration information may be RRCstate-dependent. For example, a UE in RRC connected state may receiveconfiguration information conveyed via RRC signaling and/or via physicallayer signaling (e.g., via a SIB). However, a UE that is not in RRCconnected state (e.g., a UE in RRC idle state) may only be able toreceive configuration information via physical layer signaling (e.g.,via a SIB). So in some examples, a base station may include theconfiguration information in both a SIB message and an RRC message sothat UEs in different RRC states can receive the configurationinformation. Such signaling diversity may be useful when a UE in RRCconnected state is nevertheless unable to decode an RRC message thatincludes the configuration information. For example, the UE may obtainthe configuration information from a SIB message even though it is inRRC connected state.

In some cases, a two-step RACH procedure may be configured with one ormore POs that span multiple transmission slots. In such cases, referencesignal resources for transmitting a reference signal with the firstrandom access message of the two-step RACH procedure may include atleast one symbol in each of the multiple transmission slots. In somecases, the reference signal resources within each of the multipletransmission slots may be identified based on the particular PO that isselected to transmit the first random access message. In some cases, abase station may provide system information that indicates two or moreavailable ROs and two or more available POs within each of the two ormore available ROs. In such cases, a UE may select a RO and a PO, anddetermine a reference signal sequence for a reference signal to betransmitted with the first random access message based on identifiersassociated with the selected RO and PO. In some cases, a random accesspreamble for the first random access message may be associated with theparticular reference signal resources, with the particular referencesignal sequence, or both. The RACH procedure may be configured, in somecases, based on capabilities of the UE and additional factors (e.g.,latency targets, traffic loads, number of UEs to be supported, and thelike), and the base station may select the two-step RACH procedure toprovide enhance RACH capacity, enhanced UE power saving, and synergywith other applications (e.g., positioning, mobility enhancement, etc.).

Such techniques may allow for a base station to configure random accessresources in a flexible manner based on particular objectives, such ascoverage requirements (e.g., different cell size, coverage balance ofpreamble sequence and payload info., etc.), estimated payload size,quality of service (QoS) requirements (e.g., latency, reliability,contention-based access availability for deployments that use sharedspectrum, etc.), implementation constraints of UE or base station (e.g.,radio frequency (RF) tuning gap, buffer size, processing time, etc.),emission requirements (e.g., based on adjacent channel leakage powerratio (ACLR), adjacent channel interference (ACI), etc.), orcombinations thereof. Further, such techniques may allow, in the timedomain, configurations in which the first random access message preambleand payload may be transmitted in the same or different slots.Additionally or alternatively, such techniques may allow, in the timedomain, configurations in which the first random access preamble andpayload may be transmitted in the same bandwidth, partially overlappingbandwidths, or disjoint bandwidths. Further, such techniques may allowfor enhanced resource utilization efficiency and contention mitigationwith a balanced configuration for preamble and reference signal (e.g.,demodulation reference signal (DMRS) resources in time-frequency-codedomains, and provide for relatively reliable and low-complexity UEactivity detection through associations between preamble index and DMRSresource index.

Aspects of the disclosure are initially described in the context of awireless communications system. Examples of two-step RACH procedures andreference signal configurations are then discussed with reference toexemplary systems, resources, and call flows. Aspects of the disclosureare further illustrated by and described with reference to apparatusdiagrams, system diagrams, and flowcharts that relate to referencesignal transmission techniques for random access messages.

FIG. 1 illustrates an example of a wireless communications system 100that supports reference signal transmission techniques for random accessmessages in accordance with aspects of the present disclosure. Thewireless communications system 100 includes base stations 105, UEs 115,and a core network 130. In some examples, the wireless communicationssystem 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced(LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. Insome cases, wireless communications system 100 may support enhancedbroadband communications, ultra-reliable (e.g., mission critical)communications, low latency communications, or communications withlow-cost and low-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Base stations 105 described herein mayinclude or may be referred to by those skilled in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB orgiga-NodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or some other suitable terminology. Wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro or small cell base stations). The UEs 115 describedherein may be able to communicate with various types of base stations105 and network equipment including macro eNBs, small cell eNBs, gNBs,relay base stations, and the like.

Each base station 105 may be associated with a particular geographiccoverage area 110 in which communications with various UEs 115 issupported. Each base station 105 may provide communication coverage fora respective geographic coverage area 110 via communication links 125,and communication links 125 between a base station 105 and a UE 115 mayutilize one or more carriers. Communication links 125 shown in wirelesscommunications system 100 may include uplink transmissions from a UE 115to a base station 105, or downlink transmissions from a base station 105to a UE 115. Downlink transmissions may also be called forward linktransmissions while uplink transmissions may also be called reverse linktransmissions.

The geographic coverage area 110 for a base station 105 may be dividedinto sectors making up a portion of the geographic coverage area 110,and each sector may be associated with a cell. For example, each basestation 105 may provide communication coverage for a macro cell, a smallcell, a hot spot, or other types of cells, or various combinationsthereof. In some examples, a base station 105 may be movable andtherefore provide communication coverage for a moving geographiccoverage area 110. In some examples, different geographic coverage areas110 associated with different technologies may overlap, and overlappinggeographic coverage areas 110 associated with different technologies maybe supported by the same base station 105 or by different base stations105. The wireless communications system 100 may include, for example, aheterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different typesof base stations 105 provide coverage for various geographic coverageareas 110.

The term “cell” refers to a logical communication entity used forcommunication with a base station 105 (e.g., over a carrier), and may beassociated with an identifier for distinguishing neighboring cells(e.g., a physical cell identifier (PCID), a virtual cell identifier(VCID)) operating via the same or a different carrier. In some examples,a carrier may support multiple cells, and different cells may beconfigured according to different protocol types (e.g., machine-typecommunication (MTC), narrowband Internet-of-Things (NB-IoT), enhancedmobile broadband (eMBB), or others) that may provide access fordifferent types of devices. In some cases, the term “cell” may refer toa portion of a geographic coverage area 110 (e.g., a sector) over whichthe logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile device, a wireless device, a remote device, ahandheld device, or a subscriber device, or some other suitableterminology, where the “device” may also be referred to as a unit, astation, a terminal, or a client. A UE 115 may also be a personalelectronic device such as a cellular phone, a personal digital assistant(PDA), a tablet computer, a laptop computer, or a personal computer. Insome examples, a UE 115 may also refer to a wireless local loop (WLL)station, an Internet of Things (IoT) device, an Internet of Everything(IoE) device, or an MTC device, or the like, which may be implemented invarious articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. In some examples, M2M communication or MTCmay include communications from devices that integrate sensors or metersto measure or capture information and relay that information to acentral server or application program that can make use of theinformation or present the information to humans interacting with theprogram or application. Some UEs 115 may be designed to collectinformation or enable automated behavior of machines. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). In some examples,half-duplex communications may be performed at a reduced peak rate.Other power conservation techniques for UEs 115 include entering a powersaving “deep sleep” mode when not engaging in active communications, oroperating over a limited bandwidth (e.g., according to narrowbandcommunications). In some cases, UEs 115 may be designed to supportcritical functions (e.g., mission critical functions), and a wirelesscommunications system 100 may be configured to provide ultra-reliablecommunications for these functions.

In some cases, a UE 115 may also be able to communicate directly withother UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device(D2D) protocol). One or more of a group of UEs 115 utilizing D2Dcommunications may be within the geographic coverage area 110 of a basestation 105. Other UEs 115 in such a group may be outside the geographiccoverage area 110 of a base station 105, or be otherwise unable toreceive transmissions from a base station 105. In some cases, groups ofUEs 115 communicating via D2D communications may utilize a one-to-many(1:M) system in which each UE 115 transmits to every other UE 115 in thegroup. In some cases, a base station 105 facilitates the scheduling ofresources for D2D communications. In other cases, D2D communications arecarried out between UEs 115 without the involvement of a base station105.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., via an S1, N2, N3, orother interface). Base stations 105 may communicate with one anotherover backhaul links 134 (e.g., via an X2, Xn, or other interface) eitherdirectly (e.g., directly between base stations 105) or indirectly (e.g.,via core network 130).

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC), which may include at least one mobilitymanagement entity (MME), at least one serving gateway (S-GW), and atleast one Packet Data Network (PDN) gateway (P-GW). The MME may managenon-access stratum (e.g., control plane) functions such as mobility,authentication, and bearer management for UEs 115 served by basestations 105 associated with the EPC. User IP packets may be transferredthrough the S-GW, which itself may be connected to the P-GW. The P-GWmay provide IP address allocation as well as other functions. The P-GWmay be connected to the network operators IP services. The operators IPservices may include access to the Internet, Intranet(s), an IPMultimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, mayinclude subcomponents such as an access network entity, which may be anexample of an access node controller (ANC). Each access network entitymay communicate with UEs 115 through a number of other access networktransmission entities, which may be referred to as a radio head, a smartradio head, or a transmission/reception point (TRP). In someconfigurations, various functions of each access network entity or basestation 105 may be distributed across various network devices (e.g.,radio heads and access network controllers) or consolidated into asingle network device (e.g., a base station 105).

Wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 megahertz (MHz) to 300gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known asthe ultra-high frequency (UHF) region or decimeter band, since thewavelengths range from approximately one decimeter to one meter inlength. UHF waves may be blocked or redirected by buildings andenvironmental features. However, the waves may penetrate structuressufficiently for a macro cell to provide service to UEs 115 locatedindoors. Transmission of UHF waves may be associated with smallerantennas and shorter range (e.g., less than 100 km) compared totransmission using the smaller frequencies and longer waves of the highfrequency (HF) or very high frequency (VHF) portion of the spectrumbelow 300 MHz.

Wireless communications system 100 may also operate in a super highfrequency (SHF) region using frequency bands from 3 GHz to 30 GHz, alsoknown as the centimeter band. The SHF region includes bands such as the5 GHz industrial, scientific, and medical (ISM) bands, which may be usedopportunistically by devices that may be capable of toleratinginterference from other users.

Wireless communications system 100 may also operate in an extremely highfrequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz),also known as the millimeter band. In some examples, wirelesscommunications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105, and EHF antennasof the respective devices may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115. However, the propagation of EHF transmissionsmay be subject to even greater atmospheric attenuation and shorter rangethan SHF or UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions, and designated use of bands across these frequency regions maydiffer by country or regulating body.

In some cases, wireless communications system 100 may utilize bothlicensed and unlicensed radio frequency spectrum bands. For example,wireless communications system 100 may employ License Assisted Access(LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technologyin an unlicensed band (NR-U) such as the 5 GHz ISM band. When operatingin unlicensed radio frequency spectrum bands, wireless devices such asbase stations 105 and UEs 115 may employ listen-before-talk (LBT)procedures to ensure a frequency channel is clear before transmittingdata. In some cases, operations in unlicensed bands may be based on acarrier aggregation configuration in conjunction with component carriersoperating in a licensed band (e.g., LAA). Operations in unlicensedspectrum may include downlink transmissions, uplink transmissions,peer-to-peer transmissions, or a combination of these. Duplexing inunlicensed spectrum may be based on frequency division duplexing (FDD),time division duplexing (TDD), or a combination of both.

In some examples, base station 105 or UE 115 may be equipped withmultiple antennas, which may be used to employ techniques such astransmit diversity, receive diversity, multiple-input multiple-output(MIMO) communications, or beamforming. For example, wirelesscommunications system 100 may use a transmission scheme between atransmitting device (e.g., a base station 105) and a receiving device(e.g., a UE 115), where the transmitting device is equipped withmultiple antennas and the receiving device is equipped with one or moreantennas. MIMO communications may employ multipath signal propagation toincrease the spectral efficiency by transmitting or receiving multiplesignals via different spatial layers, which may be referred to asspatial multiplexing. The multiple signals may, for example, betransmitted by the transmitting device via different antennas ordifferent combinations of antennas. Likewise, the multiple signals maybe received by the receiving device via different antennas or differentcombinations of antennas. Each of the multiple signals may be referredto as a separate spatial stream, and may carry bits associated with thesame data stream (e.g., the same codeword) or different data streams.Different spatial layers may be associated with different antenna portsused for channel measurement and reporting. MIMO techniques includesingle-user MIMO (SU-MIMO) where multiple spatial layers are transmittedto the same receiving device, and multiple-user MIMO (MU-MIMO) wheremultiple spatial layers are transmitted to multiple devices.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105 or a UE 115) to shape orsteer an antenna beam (e.g., a transmit beam or receive beam) along aspatial path between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that signals propagating atparticular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying certain amplitude and phase offsets to signals carried via eachof the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

In one example, a base station 105 may use multiple antennas or antennaarrays to conduct beamforming operations for directional communicationswith a UE 115. For instance, some signals (e.g., synchronizationsignals, reference signals, beam selection signals, or other controlsignals) may be transmitted by a base station 105 multiple times indifferent directions, which may include a signal being transmittedaccording to different beamforming weight sets associated with differentdirections of transmission. Transmissions in different beam directionsmay be used to identify (e.g., by the base station 105 or a receivingdevice, such as a UE 115) a beam direction for subsequent transmissionand/or reception by the base station 105.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit, which may, for example, refer to a sampling period ofT_(s)=1/30,720,000 seconds. Time intervals of a communications resourcemay be organized according to radio frames each having a duration of 10milliseconds (ms), where the frame period may be expressed asT_(f)=307,200 T_(s). The radio frames may be identified by a systemframe number (SFN) ranging from 0 to 1023. Each frame may include 10subframes numbered from 0 to 9, and each subframe may have a duration of1 ms. A subframe may be further divided into 2 slots each having aduration of 0.5 ms, and each slot may contain 6 or 7 modulation symbolperiods (e.g., depending on the length of the cyclic prefix prepended toeach symbol period). Excluding the cyclic prefix, each symbol period maycontain 2048 sampling periods. In some cases, a subframe may be thesmallest scheduling unit of the wireless communications system 100, andmay be referred to as a transmission time interval (TTI). In othercases, a smallest scheduling unit of the wireless communications system100 may be shorter than a subframe or may be dynamically selected (e.g.,in bursts of shortened TTIs (sTTIs) or in selected component carriersusing sTTIs).

In some wireless communications systems, a slot may further be dividedinto multiple mini-slots containing one or more symbols. In someinstances, a symbol of a mini-slot or a mini-slot may be the smallestunit of scheduling. Each symbol may vary in duration depending on thesubcarrier spacing or frequency band of operation, for example. Further,some wireless communications systems may implement slot aggregation inwhich multiple slots or mini-slots are aggregated together and used forcommunication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resourceshaving a defined physical layer structure for supporting communicationsover a communication link 125. For example, a carrier of a communicationlink 125 may include a portion of a radio frequency spectrum band thatis operated according to physical layer channels for a given radioaccess technology. Each physical layer channel may carry user data,control information, or other signaling. A carrier may be associatedwith a pre-defined frequency channel (e.g., an evolved universal mobiletelecommunication system terrestrial radio access (E-UTRA) absoluteradio frequency channel number (EARFCN)), and may be positionedaccording to a channel raster for discovery by UEs 115. Carriers may bedownlink or uplink (e.g., in an FDD mode), or be configured to carrydownlink and uplink communications (e.g., in a TDD mode). In someexamples, signal waveforms transmitted over a carrier may be made up ofmultiple sub-carriers (e.g., using multi-carrier modulation (MCM)techniques such as orthogonal frequency division multiplexing (OFDM) ordiscrete Fourier transform spread OFDM (DFT-S-OFDM)).

The organizational structure of the carriers may be different fordifferent radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR).For example, communications over a carrier may be organized according toTTIs or slots, each of which may include user data as well as controlinformation or signaling to support decoding the user data. A carriermay also include dedicated acquisition signaling (e.g., synchronizationsignals or system information, etc.) and control signaling thatcoordinates operation for the carrier. In some examples (e.g., in acarrier aggregation configuration), a carrier may also have acquisitionsignaling or control signaling that coordinates operations for othercarriers.

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using time divisionmultiplexing (TDM) techniques, frequency division multiplexing (FDM)techniques, or hybrid TDM-FDM techniques. In some examples, controlinformation transmitted in a physical control channel may be distributedbetween different control regions in a cascaded manner (e.g., between acommon control region or common search space and one or more UE-specificcontrol regions or UE-specific search spaces).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of predetermined bandwidths for carriers of a particularradio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). Insome examples, each served UE 115 may be configured for operating overportions or all of the carrier bandwidth. In other examples, some UEs115 may be configured for operation using a narrowband protocol typethat is associated with a predefined portion or range (e.g., set ofsubcarriers or RBs) within a carrier (e.g., “in-band” deployment of anarrowband protocol type).

In a system employing MCM techniques, a resource element may consist ofone symbol period (e.g., a duration of one modulation symbol) and onesubcarrier, where the symbol period and subcarrier spacing are inverselyrelated. The number of bits carried by each resource element may dependon the modulation scheme (e.g., the order of the modulation scheme).Thus, the more resource elements that a UE 115 receives and the higherthe order of the modulation scheme, the higher the data rate may be forthe UE 115. In MIMO systems, a wireless communications resource mayrefer to a combination of a radio frequency spectrum resource, a timeresource, and a spatial resource (e.g., spatial layers), and the use ofmultiple spatial layers may further increase the data rate forcommunications with a UE 115.

In some cases, a UE 115 attempting to access a wireless network mayperform an initial cell search by detecting a primary synchronizationsignal (PSS) from a base station 105. The PSS may enable synchronizationof slot timing and may indicate a physical layer identity value. The UE115 may then receive a secondary synchronization signal (SSS). The SSSmay enable radio frame synchronization, and may provide a cell identityvalue, which may be combined with the physical layer identity value toidentify the cell. The SSS may also enable detection of a duplexing modeand a cyclic prefix length. Some systems, such as TDD systems, maytransmit an SSS but not a PSS. Both the PSS and the SSS may be locatedin the central 62 and 72 subcarriers of a carrier, respectively. In somecases, a base station 105 may transmit synchronization signals (e.g.,PSS SSS, and the like) using multiple beams in a beam-sweeping mannerthrough a cell coverage area. In some cases, PSS, SSS, and/or broadcastinformation (e.g., a physical broadcast channel (PBCH)) may betransmitted within different synchronization signal blocks (SSBs) onrespective directional beams, where one or more SSBs may be includedwithin a synchronization signal (SS) burst.

After receiving the PSS and SSS, the UE 115 may receive a masterinformation block (MIB), which may be transmitted in the PBCH. The MIBmay contain system bandwidth information, an SFN, and a physical hybridautomatic repeat request (HARQ) indicator channel (PHICH) configuration.After decoding the MIB, the UE 115 may receive one or more systeminformation blocks (SIBs). For example, SIB1 may contain cell accessparameters and scheduling information for other SIBs. Decoding SIB1 mayenable the UE 115 to receive SIB2. SIB2 may contain RRC configurationinformation related to RACH procedures, paging, PUCCH, PUSCH, powercontrol, SRS, and cell barring.

After completing initial cell synchronization, a UE 115 may decode theMIB, SIB1 and SIB2 prior to accessing the network. The MIB may betransmitted on PBCH and may utilize the first 4 OFDMA symbols of thesecond slot of the first subframe of each radio frame. It may use themiddle 6 RBs (72 subcarriers) in the frequency domain. The MIB carries afew important pieces of information for UE initial access, including:downlink channel bandwidth in term of RBs, PHICH configuration (durationand resource assignment), and SFN. A new MIB may be broadcast everyfourth radio frame (SFN mod 4=0) at and rebroadcast every frame (10 ms).Each repetition is scrambled with a different scrambling code.

After reading a MIB (either a new version or a copy), the UE 115 may cantry different phases of a scrambling code until it gets a successfulcycle redundancy check (CRC). The phase of the scrambling code (0, 1, 2or 3) may enable the UE 115 to identify which of the four repetitionshas been received. Thus, the UE 115 may determine the current SFN byreading the SFN in the decoded transmission and adding the scramblingcode phase.

After receiving the MIB, a UE may receive one or more SIBs. DifferentSIBs may be defined according to the type of system informationconveyed. A new SIB1 may be transmitted in the fifth subframe of everyeighth frame (SFN mod 8=0) and rebroadcast every other frame (20 ms).SIB1 includes access information, including cell identity information,and it may indicate whether a UE is allowed to camp on a cell. SIB1 alsoincludes cell selection information (or cell selection parameters).Additionally, SIB1 includes scheduling information for other SIBs. SIB2may be scheduled dynamically according to information in SIB1, andincludes access information and parameters related to common and sharedchannels. The periodicity of SIB2 can be set to 8, 16, 32, 64, 128, 256or 512 radio frames.

After the UE 115 decodes SIB2, it may initiate a RACH procedure (e.g., atwo-step or four-step RACH procedure). In some cases, wireless devicesoperating in licensed or unlicensed spectrum within wirelesscommunications system 100 may initiate a two-step RACH procedure toreduce delay in establishing communication with a base station 105(e.g., as compared to a four-step RACH procedure). In some cases, thetwo-step RACH procedure may operate regardless of whether a wirelessdevice (e.g., a UE 115) has a valid timing advance (TA). For example, aUE 115 may use a valid TA to coordinate the timing of its transmissionsto a base station 105 (e.g., to account for propagation delay) and mayreceive the valid TA as part of the two-step RACH procedure.Additionally, the two-step RACH procedure may be applicable to any cellsize, may work regardless of whether the RACH procedure iscontention-based or contention-free, and may combine multiple RACHmessages from a four-step RACH procedure. For example, the two-step RACHprocedure may include a first message (e.g., a message A (MsgA)) thatcombines the Msg1 and Msg3 of the four-step RACH procedure and a secondmessage (e.g., a message B (MsgB)) that combines the Msg2 and Msg4 ofthe four-step RACH procedure. In some cases, the two-step RACH proceduremay result in a reduction in signaling overhead and latency, an enhancedRACH capacity, power savings for the UE 115, and provide synergy withother applications (e.g., positioning, mobility enhancement, etc.).

In some network deployment scenarios (e.g., for NR), two-step RACHprocedures and four-step RACH procedures may be used simultaneously tomeet different requirements for the system. For example, the differentrequirements may include capacity limitations, latency requirements,reliability requirements, implementation complexity specifications, etc.Accordingly, different POs may be defined that can be used for both oreither RACH procedure, and the different POs may include one or moreROs. The ROs may include time and frequency resources allocated forphysical RACH (PRACH) transmissions. Additionally, up to 64 preamblesequences may be configured for each RO. In some cases, a two-step RACHprocedure may use RACH occasions separate from a four-step RACHprocedure or may share RACH occasions with a four-step RACH procedurebut use different sets of preamble sequences. Additionally oralternatively, the POs may include time and frequency resourcesallocated for MsgA PUSCH transmissions (e.g., and/or for transmissionsassociated with the four-step RACH procedure).

In some examples of the two-step RACH procedure, a base station mayconfigure different sets of POs and/or ROs for different RRC states(e.g., the POs and/or ROs may be

RRC state-specific). For instance, the base station may configure afirst set of POs and/or ROs for a first RRC state (e.g., RRC connected)and a second set of POs and/or ROs for a second RRC state (e.g., RRCidle). In such an example, a UE may select a PO and/or RO based on thestate of the RRC state of the UE. For instance, the UE may first selectthe set of POs/ROs that is associated with (e.g., configured for) thecurrent RRC state of the UE. The UE may then select a PO/RO from the setof POs/ROs associated with the current RRC state of the UE. Thus,selection of DMRS resources may be based on the RRC state of a UE.

Wireless communications system 100 may include techniques as describedherein for two-step RACH configurations in which one or more POs mayspan multiple transmission slots, and reference signal resources fortransmitting a reference signal with the first random access message ofthe two-step RACH procedure may include at least one symbol in each ofthe multiple transmission slots. In some cases, the reference signalresources within each of the multiple transmission slots may beidentified based on the particular PO that is selected to transmit thefirst random access message. In some cases, a base station 105 mayprovide system information that indicates two or more available ROs andtwo or more available POs within each of the two or more available ROs.In such cases, a UE 115 may select a RO and a PO, and determine areference signal sequence for a reference signal to be transmitted withthe first random access message based on identifiers associated with theselected RO and PO. In some cases, a random access preamble for thefirst random access message may be associated with the particularreference signal resources, with the particular reference signalsequence, or both.

FIG. 2 illustrates an example of a wireless communications system 200that supports reference signal transmission techniques for random accessmessages in accordance with aspects of the present disclosure. In someexamples, wireless communications system 200 may implement aspects ofwireless communications system 100. Wireless communications system 200may include a base station 105-a and a UE 115-a, which may be examplesof corresponding base stations 105 and UEs 115, respectively, asdescribed above with reference to FIG. 1. In some cases, UE 115-a mayperform a RACH procedure to connect with base station 105-a as part ofan initial cell selection, a cell reselection, or a similar accessprocedure. Accordingly, base station 105-a may transmit downlinkmessages to UE 115-a on resources of a carrier 205-a, and UE 115-a maytransmit uplink messages to base station 105-a on resources of a carrier205-b. In some cases, carriers 205-a and 205-b may be a same carrier ormay be separate carriers. For example, base station 105-a may broadcastthe downlink messages on time and frequency resources reserved forbroadcasted transmissions, which may be different than resourcesallocated for uplink messages from UE 115-a or other UEs 115 in thecoverage area of base station 105-a. Additionally or alternatively, UE115-a may be in a connected state (e.g., RRC_CONNECTED state) with basestation 105-a, and downlink messages and uplink messages may betransmitted on a same carrier established previously.

As described herein, UE 115-a may perform a two-step RACH procedure toestablish a connection with base station 105-a (e.g., initialconnection, reestablishment, etc.). Accordingly, base station 105-a maytransmit configuration information 210 to provide one or moreconfigurations for UE 115-a to transmit different portions of a firstmessage 220 (e.g., MsgA) of the two-step RACH procedure. For example,first message 220 may include a preamble 225 and a payload 230, andconfiguration information 210 may provide configurations for ROs and POsof two-step RACH procedures for UE 115-a to transmit preamble 225 andpayload 230, respectively (e.g., preamble 225 is transmitted in a RACHoccasion and payload 230 is transmitted in a PUSCH occasion). Responsiveto the first message 220, the base station 105-a may transmit a secondmessage 215 (e.g., msgB) which may include a response to the firstmessage 220.

Before transmitting first message 220 with preamble 225 and payload 230,UE 115-a may determine a first message configuration based on theconfiguration information 210. Based on first message configuration, UE115-a may select a PO and RO for the first message 220. In some cases,base station 105-a may transmit configuration information 210 in an SItransmission (e.g., if UE 115-a is not connected to base station 105-a).Additionally or alternatively, if UE 115-a is in a connected state(e.g., RRC_CONNECTED state) with base station 105-a, base station 105-amay transmit configuration information 210 via one or both of SI or RRCsignaling (e.g., which may provide a higher degree of flexibility inresource allocations). For example, the different occasions to transmitconfiguration information 210 may provide more techniques for basestation 105-a to indicate resource allocations for transmitting preamble225 and/or payload 230.

Additionally, UE 115-a may determine time and frequency resources fortransmitting preamble 225 and payload 230. In the time domain, UE 115-amay transmit preamble 225 and payload 230 of first message 220 within asame slot or on different slots. For example, configuration information210 may include a set of preamble formats that UE 115-a can use forpreamble 225 and a configurable transmission gap that enables whetherpreamble 225 and payload 230 are transmitted within a same slot or not.Each preamble format or subsets of the preamble formats may correspondto different time and frequency resources, which may indicate whenpayload 230 can be transmitted after preamble 225. Additionally, thetransmission gap may indicate a time duration between transmittingpreamble 225 and transmitting payload 230, which may result in payload230 being transmitted in a separate slot than preamble 225 if thetransmission gap is long enough to extend into the separate slot. In thefrequency domain, UE 115-a may transmit preamble 225 and payload 230 offirst message 220 in a same bandwidth, in partially overlappingbandwidths, or in disjoint bandwidths based on information inconfiguration information 210. For example, base station 105-a mayconfigure ROs and POs for the respective portions of first message 220with a same bandwidth or partially overlapping bandwidths.

In some cases, each RO may be associated with one or multiple POs. Forexample, one RO may be associated with multiple POs, where differentsubsets of RACH preambles in the RO correspond to one or multiple POs(e.g., a first RACH preamble subset may correspond to a first resourceset that includes one or more POs, and a second RACH preamble subset maycorrespond to a second resource set that includes one or more different(e.g., or overlapping) POs). Each PO in a respective resource set mayinclude a same modulation and coding scheme (MCS), payload size, andwaveform configuration. Base station 105-a may configure the associationbetween the ROs and the POs based on partitioning in the code domain(e.g., by preamble sequence groupings with the different preamblesubsets). Accordingly, base station 105-a may indicate different subsetsof preambles are associated with different POs configurations (e.g.,resource sets with same MCS, payload size, and waveform configurations)in configuration information 210.

Additionally, as described above, in cases where two-step RACHconfigurations include one or more POs that span multiple transmissionslots, reference signal resources for transmitting a reference signalwith the first message 220 may include at least one symbol in each ofthe multiple transmission slots. In some cases, the reference signalresources within each of the multiple transmission slots may beidentified based on the particular PO that is selected to transmit thefirst message 220. In some cases, a base station 105-a may providesystem information that indicates two or more available ROs, and two ormore available POs within each of the two or more available ROs. In suchcases, UE 115-a may select a RO and a PO, and determine a referencesignal sequence for a reference signal to be transmitted with the firstmessage 220 based on identifiers associated with the selected RO and PO.In some cases, the random access preamble for the first message 220 maybe associated with the particular reference signal resources, with theparticular reference signal sequence, or both.

For example, in some cases multiple demodulation reference signal (DMRS)symbols can be configured per PO (i.e., N>1 DMRS symbols per PO), andthe DMRS symbol location can be front-loaded within each slot,distributed within each slot, or combinations thereof. Further, if thePO spans K slots (i.e., K>1), the number of DMRS symbols within eachslot can be the same or different (e.g., K=2, N=4 where two slots eachhave two DMRS symbols, or K=2, N=3 where a first slot has two DMRSsymbols while a second slot has one DMRS symbol). In such cases, thereference signal resources may be distributed across slots, and multiplereference signal symbols may be configured within one or more of theslots. In some cases, particular RACH preambles may be associated withdifferent reference signal resources, which may assist the base station105-a in identifying transmissions of the UE 115-a. Such referencesignal resource may allow for more reliable demodulation of the firstmessage 220, which may enhance efficiency, latency, and reliability ofthe wireless communications system 200.

Additionally, in some cases, an orthogonal cover code (OCC) may beapplied to the first message 220. An OCC may allow the base station105-a to decode concurrent transmissions of multiple UEs 115 throughmultiple access techniques (e.g., non-orthogonal multiple access (NOMA)successive interference cancellation (SIC) and multi-user decoding (MUD)techniques). In some cases, an OCC may be applied to a reference signal,which may be extended across multiple DMRS symbols per PO, which mayallow for enhanced reliability in detection of the DMRS. In some cases,the OCC may be a binary OCC, a non-binary OCC, or quasi-orthogonalsequence, that may be configured based on the configuration information210. In some cases, the OCC may be selected from an OCC codebook (e.g.,one or more tables that map particular OCCs to RACH preambles, POs, ROs,DMRS resources, or any combinations thereof). In some cases, one ormultiple OCC codebooks may be configured by the configurationinformation 210. In some cases, an OCC extension may be applied acrossall DMRS symbols of a PO as provided in a single OCC codebook. In othercases, multiple OCC codebooks may be provided, and DMRS symbols within aPO can be grouped into multiple subsets in which one OCC is specifiedfor each subset individually, and different OCC codebooks can beconfigured with similar of different alphabets (e.g., binary,non-binary, or a hybrid of binary and non-binary). Additionally, OCCextension may be separately or jointly considered in frequency domain.

As discussed herein, payload 230 of the first message 220 may includeDMRS symbols, and in some cases DMRS sequences for the DMRS symbols maybe selected based on the particular PO, RO, or combinations thereof,that are selected for the first message 220 transmission. For example,for a given number of DMRS symbols per PO, DMRS sequence generation beperformed according to a generation formula that is a function of aresource index of the PO, RO, or combinations thereof. For example, insome cases PUSCH transmissions may use a cyclic prefix OFDM (CP-OFDM)waveform, and DMRS sequences may be generated based on a gold sequenceor other pseudo0noins (PN) PN sequences with closed-form generatorpolynomials. In such cases, a resource index of the selected PO, RO, aRACH preamble sequence index, or any combinations thereof may be used todetermine the DMRS sequence. For example, if a closed-form polynomialgenerator is used to generate the DMRS sequence, an initialization seed(c_(init)) of the polynomial generator may be based on the one or moreindex values. In one specific example, the initialization seed may bedetermined according to:c _(init)

(2¹⁷(N _(symb) ^(slot) n _(s,f) ^(μ) +l+1)(N _(ID) ²+1)mod 2³¹where

-   (1) N _(ID) ²    (2N _(ID) ^(cell) +K ₁ ·P _(ID) +K ₂ ·R _(ID) +K ₃ ·S _(ID))mod    65535 and K_(i)≥0 are scaling constants, i=1, 2, 3;-   (2) l is the OFDM symbol index within the slot carrying DMRS    symbols;-   (3) n_(s,f) ^(μ) is the slot number within a frame with subcarrier    spacing (SCS) configuration μ; and-   (4) P_(ID), R_(ID), and S_(ID) denote the index of PO, RO and    preamble sequence in use, respectively.

In other cases, PUSCH transmissions may use a DFT-s-OFDM waveform, andDMRS sequences may be generated based on defined base sequences {r_(u,v)^(α)}In addition, in some cases, Zadoff-Chu (ZC) sequences, computergenerated sequences (CGS), modified chirp sequences, or other compositelow peak-to-average-power (PAPR) sequences may be configured in theconfiguration information 210. In some cases, the base sequences may bedivided into multiple groups, with u denoting the group number and vdenoting the base sequence within a given group. In some cases, thegroup index u, sequence index v, a cyclic shift α, or any combinationsthereof may be formulated as a function of one or more of P_(ID),R_(ID), or S_(ID). For example:u

(f _(gh) +n _(ID) ^(RS,2))mod Q, where

-   (1) n_(ID) ^(RS,2)    (K₄·P_(ID)+K₅·R_(ID)+K₆·S_(ID));-   (2) P_(ID), R_(ID), and S_(ID) denote the index of PO, RO and    preamble sequence in use, respectively;-   (3) K_(i)≥0 are scaling constants, i=4, 5, 6;-   (4) Q is a constant (e.g., Q=30);-   (5) f_(gh) denotes a hopping mode index, which may be jointly    defined with sequence index v, and, if neither group or sequence    hopping is enabled: f_(gh)=v=0, and if group hopping is enabled and    sequence hopping is disabled, the initialization seed of PN sequence    c(i) can be initialized with:    c_(init)=    └n_(ID) ^(R,S2)/30┘ and    f _(gh)=(ρ_(m=0) ⁷2^(m) c(8(N _(symb) ^(slot) n _(s,f) ^(μ)    +l)+m))mod 30    v=0    Further. if group hopping is disabled and sequence hopping is    enabled, the initialization seed of PN sequence c(i) can be    initialized with

$c_{init}\overset{\Delta}{=}{n_{ID}^{{RS},2}\mspace{14mu}{and}}$f_(gh) = 0 $v = \{ \begin{matrix}{c( {{N_{symb}^{slot}n_{s,f}^{\mu}} + l} )} & {{{if}\mspace{14mu} M_{ZC}} \geq {6N_{sc}^{RB}}} \\{0\mspace{149mu}} & {{otherwise}\mspace{59mu}}\end{matrix} $

FIG. 3 illustrates an example of a process flow 300 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. In some examples,process flow 300 may implement aspects of wireless communications system100 or 200. Process flow 300 may include a base station 105-b and a UE115-b, which may be examples of corresponding base stations 105 and UEs115, respectively, as described above with reference to FIGS. 1-2.Additionally, process flow 300 may illustrate a two-step RACH procedureas described herein for UE 115-a to establish a connection with basestation 105-b for subsequent communications.

At 305, base station 105-a may transmit a synchronization signal block(SSB), system information block (SIB), reference signal (RS), or acombination thereof to indicate configuration information to UE 115-bfor performing the two-step RACH procedure.

At 310, UE 115-b may perform a downlink synchronization based on thereceived SSB to synchronize with base station 105-b prior to beginningthe two-step RACH procedure. Additionally, UE 115-b may decode andmeasure any SI transmissions received from base station 105-b (e.g.,SIB, RS, etc.) to identify configuration information for transmitting afirst message of the two-step RACH procedure. For example, by decodingand measuring the SI, UE 115-b may identify a periodicity fortransmitting different portions of the first message.

At 315, UE 115-b may transmit, to base station 105-b, the first randomaccess message (e.g., msgA) of the two-step RACH procedure. The firstrandom access message may include a preamble (e.g., MsgA preamble)transmitted in one or more ROs configured by the base station 105-b tocarry the preamble. Additionally, the first random access message mayinclude a payload (e.g., MsgA payload), where the payload is transmittedin one or more POs associated with the RO as described herein. Thepayload may include one or more DMRS symbols that are determined basedat least in part on the RO, PO, or combinations thereof. Further, theDMRS sequence may be determined based at least in part on the RO, PO, orcombinations thereof.

At 320, base station 105-b may process the preamble of the first randomaccess message. Accordingly, if the preamble is detected and intendedfor base station 105-b from UE 115-b, at 325, base station 105-b maythen process the payload of the first random access message.

Based on correctly receiving and processing both portions of the firstrandom access message, at 330, base station 105-b may then transmit asecond random access message (e.g., MsgB) of the two-step RACH procedureto UE 115-b. Subsequently, if UE 115-b correctly receives the secondrandom access message (e.g., with no interference or is able to decodethe message with any interference), the two-step RACH procedure may becomplete, and UE 115-b and base station 105-b may communicate based onthe successful RACH procedure.

FIG. 4A illustrates an example of a channel structure 400 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. In some examples,channel structure 400 may implement aspects of wireless communicationssystem 100 or 200. In some cases, channel structure 400 may representthe structure of a first message 405 (e.g., MsgA) for a two-step RACHprocedure as described herein. Accordingly, in some cases, a UE 115 maytransmit first message 405 to a base station 105 according to thechannel structure 400. The channel structure 400 of the first message405 may support a contention-based random access (CBRA) (e.g., RACH)procedure on shared time-frequency-code resources

In some cases, first message 405 may include a preamble 410 and apayload 415 as described above, where transmission bandwidths for thepreamble 410 and the payload 415 may be the same or different. Thepreamble 410 may include a PRACH preamble signal 420, where the preamble410 (e.g., with PRACH preamble signal 420) serves multiple purposes. Forexample, the preamble 410 may facilitate timing offset estimation by thebase station 105. Additionally, the preamble 410 may supply an earlyindication of MCS, payload size, and resource allocation for the payload415 (e.g., which may provide a more efficient solution than an uplinkcontrol information (UCI) piggyback on a PUSCH that includes thepayload). In some cases, the resource allocation for the payload 415 maybe based on a pre-defined mapping rule between the preamble 410 and thepayload 415 that is indicated in configuration information from the basestation 105. The payload 415 may include a DMRS/PUSCH 435 portion fortransmission of the payload of the first message 405, where the payload415 may include a configurable payload size for different use cases andRRC states. For example, the payload 415 may include a minimum payloadsize (e.g., of 56/72 bits) and may not include a maximum (e.g., upperbound) payload size. In some cases, the payload 415 may include 1000bits of small data from a user plane (UP) and/or control plane (CP).

Additionally, between each portion of first message 405 (e.g., betweenpreamble 410 and payload 415), a guard time (GT) 425 may exist. Forexample, the base station 105 may configure the GT 425 to mitigate intersymbol interference (ISI) and/or inter carrier interference (ICI) forasynchronous uplink communications. In some cases, GT 425 may bereferenced as a guard band (GB). A first GT 425-a may exist betweenpreamble 410 and payload 415, and a second GT 425-b may exist afterpayload 415 and a subsequent preamble 410. Additionally, the basestation 105 may also configure a transmission gap (e.g., TxG) 430 toextend the time between preamble 410 and payload 415. The transmissiongap 430 may extend the first message 405 to occur over more than onesymbol (e.g., or different TTI length). In some cases, each GT 425 mayhave a duration equal to T_(G), and the transmission gap 430 may have aduration equal to T_(g).

FIG. 4B illustrates an example of a transmit chain 401 that supportstwo-step RACH in accordance with aspects of the present disclosure. Insome examples, transmit chain 401 may implement aspects of wirelesscommunications systems 100 or 200. Transmit chain 401 may illustrate howa first message of a two-step RACH procedure (e.g., MsgA) is configured(e.g., encoded, scrambled, mapped, etc.) by a UE 115 prior to the UE 115transmitting the first message.

The UE 115 may use an encoder 440 for encoding a payload portion of thefirst message. In some cases, the encoder 440 may be a low-densityparity check (LDPC) encoder. After encoding the payload, the UE 115 maypass the payload through a scrambling 445, which may scramble theencoded bits. After scrambling the encoded bits, the UE 115 may thenperform modulation 450. In some cases, the modulation 450 may include alinear modulation. Subsequently, the UE 115 may perform a precoding 455(e.g., transform precoding) on the modulated bits. The UE 115 may thenuse an inverse fast Fourier transform (IFFT) 460 after precoding totransform the bits. After the IFFT 460, the UE 115 may use a multiplexer(MUX) 465. In some cases, with the multiplexer 465, the UE 115 maymultiplex a DMRS 435 (e.g., in reference signal resources and using aDMRS sequence as described herein). Subsequently, the UE 115 may performa mapping 470. In some cases, the UE 115 may perform the mapping asbased at least in part on the preamble 410 (e.g., as referenced by thepreamble 410 in FIG. 4A). For example, the preamble 410 may indicate apre-defined mapping rule between a preamble and the payload, referencesignal resources, OCC, and/or reference signal sequence, of the firstmessage. The UE 115 may then transmit the first message after performingthe different steps.

FIG. 5 illustrates an example of a slot structure 500 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. In some examples,slot structure 500 may implement aspects of wireless communicationssystem 100 or 200. As indicated with reference to FIGS. 1 through 4, insome cases a PO may span multiple slots, and DMRS resources may beconfigured in each of the slots in accordance with techniques asdiscussed herein.

In the example of FIG. 5, a first slot 505 (slot A) and a second slot515 (slot B) may be configured in a selected PO. Within each of thefirst slot 505 and the second slot 515, multiple DMRS symbols 510 may beconfigured (i.e., N>1 DMRS symbols 510 per PO). The DMRS symbol 510locations may be front-loaded within each slot, distributed within eachslot, or combinations thereof. In the example of FIG. 5, a first DMRSsymbol 510-a and a second DMRS symbol 510-b may be front loaded withinthe first slot 505, and a third DMRS symbol 510-c and a fourth DMRSsymbol 510-a may be distributed within the second slot 515. While a samenumber of DMRS symbols 510 are illustrated in each slot in this example,in other cases the number of DMRS symbols 510 within each slot can bedifferent (e.g., K=2, N=3 where a first slot has two DMRS symbols whilea second slot has one DMRS symbol). In some cases, particular RACHpreambles may be associated with different reference signal resources,which may assist the base station in identifying transmissions of theUE. In some cases, an OCC may be applied to the slot structure 500 inaccordance with techniques such as discussed with reference to FIG. 2.

FIG. 6 illustrates an example of a process flow 600 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. In some examples,process flow 600 may implement aspects of wireless communications system100 or 200. Process flow 600 may include a base station 105-c and a UE115-c, which may be examples of corresponding base stations 105 and UEs115, respectively, as described above with reference to FIGS. 1-5.

In the following description of the process flow 600, the operationsbetween UE 115-c and base station 105-c may be transmitted in adifferent order than the order shown, or the operations performed bybase station 105-c and UE 115-c may be performed in different orders orat different times. Certain operations may also be left out of theprocess flow 600, or other operations may be added to the process flow600. It is to be understood that while base station 105-c and UE 115-care shown performing a number of the operations of process flow 600, anywireless device may perform the operations shown.

At 605, the base station 105-c may transmit, and the UE 115-c mayreceive, a configuration message for a two-step RACH procedure. In somecases, the configuration message may include configuration informationfor transmission of a preamble and transmission of a payload (e.g.,configured ROs, POs, preamble sequences, DMRS resource/sequences, etc.),the preamble and the payload associated with a first message of thetwo-step RACH procedure (e.g., MsgA). In some cases, the UE 115-c mayreceive the configuration message via RRC signaling or via an SItransmission.

At 610, UE 115-c may select a particular RO and PO for transmission of afirst message. In some cases, UE 115-c may select the RO/PO based on anamount of data that is to be transmitted in the first message, forexample. In some cases, the configuration message may include anindication of a subset of ROs and POs from which the UE 115-c may makesuch a selection.

At 615, the UE 115-c may identify DMRS resources for the first randomaccess message. For example, the UE 115-c may identify DMRS resourcesfor DMRS transmissions in a payload portion of the first random accessmessage. In some cases, the UE 115-c may select a random access preamblefor the first random access message (e.g., based on a set of availableRACH preambles configured by the base station 105-c for the UE 115-c),and the DMRS resources may be associated with a particular preamble. Insome cases, the DMRS resources may be determined based on the particularPO that is selected for transmission of the payload. In some cases, thePO may span multiple slots, and the DMRS resources also may span themultiple slots. In some cases, the DMRS resources may be front loadedwithin one or more of the slots, distributed in one or more of theslots, of combinations thereof.

At 620, the UE 115-c may format the first random access message. In somecases, the first random access message may be formatted with a selectedpreamble and payload that are determined based on the configurationinformation provided by the base station 105-c. Further, the payload mayinclude reference signal transmissions in accordance with the techniquesdiscussed herein.

At 625, UE 115-c may transmit, to base station 105-c, the first randomaccess message, which may include the preamble and payload. In somecases, UE 115-c may transmit the preamble, and them may transmit thepayload after an identified transmission gap. Additionally, the preambleand the payload of the first message may be transmitted within a sameslot or on different slots. In some cases, the preamble and the payloadof the first message also may be transmitted within a same bandwidth,partially overlapping bandwidths, or disjoint bandwidths.

At 630, the base station 105-c may receive the first message. In somecases, the base station 105-c may perform preamble detection, and thenperform payload processing based at least in part on whether thepreamble of the UE 115-c is successfully detected. At 635, the basestation 105-c may format a second random access message (e.g., msgB),and at 640 may transmit the second random access message to the UE115-c. In some cases, the second random access message may includeinformation to establish or reestablish a RRC connection.

FIG. 7 illustrates an example of a process flow 700 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. In some examples,process flow 700 may implement aspects of wireless communications system100. Process flow 700 may include a base station 105-d and a UE 115-d,which may be examples of corresponding base stations 105 and UEs 115,respectively, as described above with reference to FIGS. 1-6.

In the following description of the process flow 700, the operationsbetween UE 115-d and base station 105-d may be transmitted in adifferent order than the order shown, or the operations performed bybase station 105-d and UE 115-d may be performed in different orders orat different times. Certain operations may also be left out of theprocess flow 700, or other operations may be added to the process flow700. It is to be understood that while base station 105-d and UE 115-dare shown performing a number of the operations of process flow 700, anywireless device may perform the operations shown.

At 705, the base station 105-d may transmit, and the UE 115-d mayreceive, a configuration message for a two-step RACH procedure. In somecases, the configuration message may include configuration informationfor transmission of a preamble and transmission of a payload (e.g.,configured ROs, POs, preamble sequences, DMRS resource/sequences, etc.),the preamble and the payload associated with a first message of thetwo-step RACH procedure (e.g., MsgA). In some cases, the UE 115-d mayreceive the configuration message via RRC signaling or via an SItransmission.

At 710, UE 115-d may select a particular RO for transmission of a firstmessage. In some cases, UE 115-d may select the RO based on informationin the configuration message, such as a subset of ROs that are availablefor selection by the UE 115-d. In some cases, one or more ROs mayinclude multiple POs, and at 715, the UE 115-d may select a PO fromavailable POs for the selected RO. In some cases, for example, the POmay be selected based on an amount of data that is to be transmitted inthe first message.

At 720, the UE 115-d may determine a DMRS sequence for a payload portionof a first random access message. In some cases, the DMRS sequence maybe selected based at least in part on one or more of an index of theselected RO, an index of the selected PO, a preamble index of a selectedpreamble, or any combinations thereof. In some cases, the DMRS sequencemay be determined based on an initialization seed that is a function ofthe RO index, PO index, preamble index, or combinations thereof, asdiscussed herein.

At 725, the UE 115-d may format the first random access message. In somecases, the first random access message may be formatted with a selectedpreamble and payload that are determined based on the configurationinformation provided by the base station 105-d. Further, the payload mayinclude DMRS symbols and DMRS sequences in accordance with thetechniques discussed herein.

At 730, UE 115-d may transmit, to base station 105-d, the first randomaccess message, which may include the preamble and payload. In somecases, UE 115-d may transmit the preamble, and them may transmit thepayload after an identified transmission gap. Additionally, the preambleand the payload of the first message may be transmitted within a sameslot or on different slots. In some cases, the preamble and the payloadof the first message also may be transmitted within a same bandwidth,partially overlapping bandwidths, or disjoint bandwidths.

At 735, the base station 105-d may receive the first message. In somecases, the base station 105-d may perform preamble detection, and thenperform payload processing based at least in part on whether thepreamble of the UE 115-d is successfully detected. At 740, the basestation 105-d may format a second random access message (e.g., msgB),and at 745 may transmit the second random access message to the UE115-d. In some cases, the second random access message may includeinformation to establish or reestablish a RRC connection.

FIG. 8 shows a block diagram 800 of a device 805 that supports referencesignal transmission techniques for random access messages in accordancewith aspects of the present disclosure. The device 805 may be an exampleof aspects of a UE 115 as described herein. The device 805 may include areceiver 810, a communications manager 815, and a transmitter 820. Thedevice 805 may also include a processor. Each of these components may bein communication with one another (e.g., via one or more buses).

The receiver 810 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to referencesignal transmission techniques for random access messages, etc.).Information may be passed on to other components of the device 805. Thereceiver 810 may be an example of aspects of the transceiver 1120described with reference to FIG. 11. The receiver 810 may utilize asingle antenna or a set of antennas.

The communications manager 815 may receive system information from abase station, the system information including an indication of two ormore available uplink shared channel transmission occasions for a randomaccess message transmission from the UE, select a first uplink sharedchannel transmission occasion of the two or more available uplink sharedchannel transmission occasions for transmission of a first random accessmessage, where the first uplink shared channel transmission occasionspans at least two transmission slots, determine, based on the systeminformation, reference signal resources within the first uplink sharedchannel transmission occasion for transmitting a reference signal withthe first random access message, where the reference signal resourcesinclude at least one symbol in each of the two or more transmissionslots, format the first random access message based on the selectedfirst uplink shared channel transmission occasion and the identifiedreference signal resources, the first random access message includingthe reference signal and uplink shared channel data, and transmit thefirst random access message to the base station.

The communications manager 815 may also receive system information froma base station, the system information including an indication of two ormore available random access occasions and two or more available uplinkshared channel transmission occasions within each of the two or moreavailable random access occasions, where each of the two or moreavailable random access occasions is indicated by an associated randomaccess occasion identifier and each of the two or more available uplinkshared channel transmission occasions is indicated by an associateduplink shared channel transmission occasion identifier, select a firstrandom access occasion of the two or more available random accessoccasions and a first uplink shared channel transmission occasion of thetwo or more available uplink shared channel transmission occasions fortransmission of a first random access message, determine, based on afirst random access occasion identifier associated with the first randomaccess occasion, a first uplink shared channel transmission occasionidentifier associated with the first uplink shared channel transmissionoccasion, or combinations thereof, a reference signal sequence for areference signal to be transmitted with the first random access message,and transmit the first random access message to the base station. Thecommunications manager 815 may be an example of aspects of thecommunications manager 1110 described herein.

Based on the actions performed by the communications manager 815 asdescribed herein, a UE 115 may transmit a first message of a two-stepRACH procedure with a reference signal in determined resources having areference signal sequence as determined in accordance with varioustechniques provided herein. Such techniques may provide for enhancedreference signal transmissions that may allow for more reliablereception and decoding of random access messages, thereby enhancingsystem efficiency and reliability. Further, latency may also be reducedwith the base station receiving and decoding payloads more reliably.

The communications manager 815, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the communications manager 815, or itssub-components may be executed by a general-purpose processor, a digitalsignal processor (DSP), an application-specific integrated circuit(ASIC), a field-programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed in the present disclosure.

The communications manager 815, or its sub-components, may be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations byone or more physical components. In some examples, the communicationsmanager 815, or its sub-components, may be a separate and distinctcomponent in accordance with various aspects of the present disclosure.In some examples, the communications manager 815, or its sub-components,may be combined with one or more other hardware components, includingbut not limited to an input/output (I/O) component, a transceiver, anetwork server, another computing device, one or more other componentsdescribed in the present disclosure, or a combination thereof inaccordance with various aspects of the present disclosure.

The transmitter 820 may transmit signals generated by other componentsof the device 805. In some examples, the transmitter 820 may becollocated with a receiver 810 in a transceiver module. For example, thetransmitter 820 may be an example of aspects of the transceiver 1120described with reference to FIG. 11. The transmitter 820 may utilize asingle antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a device 905 that supports referencesignal transmission techniques for random access messages in accordancewith aspects of the present disclosure. The device 905 may be an exampleof aspects of a device 805, or a UE 115 as described herein. The device905 may include a receiver 910, a communications manager 915, and atransmitter 950. The device 905 may also include a processor. Each ofthese components may be in communication with one another (e.g., via oneor more buses).

The receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to referencesignal transmission techniques for random access messages, etc.).Information may be passed on to other components of the device 905. Thereceiver 910 may be an example of aspects of the transceiver 1120described with reference to FIG. 11. The receiver 910 may utilize asingle antenna or a set of antennas.

The communications manager 915 may be an example of aspects of thecommunications manager 815 as described herein. The communicationsmanager 915 may include a system information manager 920, a PO manager925, a reference signal resource manager 930, a random access messagemanager 935, a RO manager 940, and a reference signal sequence manager945. The communications manager 915 may be an example of aspects of thecommunications manager 1110 described herein.

The system information manager 920 may receive system information from abase station, the system information including an indication of two ormore available uplink shared channel transmission occasions for a randomaccess message transmission from the UE.

The PO manager 925 may select a first uplink shared channel transmissionoccasion of the two or more available uplink shared channel transmissionoccasions for transmission of a first random access message, where thefirst uplink shared channel transmission occasion spans at least twotransmission slots.

The reference signal resource manager 930 may determine, based on thesystem information, reference signal resources within the first uplinkshared channel transmission occasion for transmitting a reference signalwith the first random access message, where the reference signalresources include at least one symbol in each of the two or moretransmission slots.

The random access message manager 935 may format the first random accessmessage based on the selected first uplink shared channel transmissionoccasion and the determined reference signal resources, the first randomaccess message including the reference signal and uplink shared channeldata and transmit the first random access message to the base station.

In some cases, the system information manager 920 may receive systeminformation from a base station, the system information including anindication of two or more available random access occasions and two ormore available uplink shared channel transmission occasions within eachof the two or more available random access occasions, where each of thetwo or more available random access occasions is indicated by anassociated random access occasion identifier and each of the two or moreavailable uplink shared channel transmission occasions is indicated byan associated uplink shared channel transmission occasion identifier.The RO manager 940 may select a first random access occasion of the twoor more available random access occasions and a first uplink sharedchannel transmission occasion of the two or more available uplink sharedchannel transmission occasions for transmission of a first random accessmessage. The reference signal sequence manager 945 may determine, basedon a first random access occasion identifier associated with the firstrandom access occasion, a first uplink shared channel transmissionoccasion identifier associated with the first uplink shared channeltransmission occasion, or combinations thereof, a reference signalsequence for a reference signal to be transmitted with the first randomaccess message. The random access message manager 935 may transmit thefirst random access message to the base station.

Based on receiving the system information, a processor of a UE 115(e.g., controlling the receiver 910, the transmitter 950, or atransceiver 1120 as described with reference to FIG. 11) may efficientlyprepare a preamble and payload of a first message of a two-step RACHprocedure prior to transmitting each of the preamble and the payload.For example, the processor of the UE 115 may determine whencorresponding RACH occasions and PUSCH occasions are forthcoming fortransmitting the preamble and the payload, respectively, and transmitthe corresponding transmissions with reference signals to aid inreception and demodulation of the random access messages in an efficientand reliable manner.

The transmitter 950 may transmit signals generated by other componentsof the device 905. In some examples, the transmitter 950 may becollocated with a receiver 910 in a transceiver module. For example, thetransmitter 950 may be an example of aspects of the transceiver 1120described with reference to FIG. 11. The transmitter 950 may utilize asingle antenna or a set of antennas.

FIG. 10 shows a block diagram 1000 of a communications manager 1005 thatsupports reference signal transmission techniques for random accessmessages in accordance with aspects of the present disclosure. Thecommunications manager 1005 may be an example of aspects of acommunications manager 815, a communications manager 915, or acommunications manager 1110 described herein. The communications manager1005 may include a system information manager 1010, a PO manager 1015, areference signal resource manager 1020, a random access message manager1025, a random access preamble manager 1030, a reference signal sequencemanager 1035, a RO manager 1040, and a polynomial generator 1045. Eachof these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses).

The system information manager 1010 may receive system information froma base station, the system information including an indication of two ormore available uplink shared channel transmission occasions for a randomaccess message transmission from the UE.

In some examples, the system information manager 1010 may receive systeminformation from a base station, the system information including anindication of two or more available random access occasions and two ormore available uplink shared channel transmission occasions within eachof the two or more available random access occasions, where each of thetwo or more available random access occasions is indicated by anassociated random access occasion identifier and each of the two or moreavailable uplink shared channel transmission occasions is indicated byan associated uplink shared channel transmission occasion identifier.

The PO manager 1015 may select a first uplink shared channeltransmission occasion of the two or more available uplink shared channeltransmission occasions for transmission of a first random accessmessage, where the first uplink shared channel transmission occasionspans at least two transmission slots.

The reference signal resource manager 1020 may determine, based on thesystem information, reference signal resources within the first uplinkshared channel transmission occasion for transmitting a reference signalwith the first random access message, where the reference signalresources include at least one symbol in each of the two or moretransmission slots. In some cases, the reference signal is ademodulation reference signal, and where the reference signal resourcesin each of the two or more transmission slots are front-loaded in eachof the at least two transmission slots, are distributed in each of theat least two transmission slots, or combinations thereof.

The random access message manager 1025 may format the first randomaccess message based on the selected first uplink shared channeltransmission occasion and the determined reference signal resources, thefirst random access message including the reference signal and uplinkshared channel data. In some examples, the random access message manager1025 may transmit the first random access message to the base station.

The reference signal sequence manager 1035 may determine, based on afirst random access occasion identifier associated with the first randomaccess occasion, a first uplink shared channel transmission occasionidentifier associated with the first uplink shared channel transmissionoccasion, or combinations thereof, a reference signal sequence for areference signal to be transmitted with the first random access message.In some examples, the reference signal sequence manager 1035 maydetermine a reference signal sequence for the reference signal based onthe random access preamble.

In some examples, the reference signal sequence manager 1035 may apply acover code to the reference signal that is associated with the UE. Insome examples, the reference signal sequence manager 1035 may determinethe cover code based on a codebook indicated by the system information,and where the cover code spans all of the reference signal resources ineach of the two or more transmission slots. In some examples, thereference signal sequence manager 1035 may determine separate covercodes associated with each of the two or more transmission slots basedon different codebooks associated with each of the two or moretransmission slots. In some cases, the cover code is a binary orthogonalcover code, a non-binary orthogonal cover code, or a quasi-orthogonalcover code. In some cases, the different codebooks are each associatedwith different subsets of the two or more available uplink sharedchannel transmission occasions. In some cases, the cover code is appliedseparately or jointly across frequency domain resources associated withthe two or more available uplink shared channel transmission occasions.

In some examples, the reference signal sequence manager 1035 maydetermine an initialization seed for a polynomial generator thatgenerates the reference signal sequence, the initialization seed basedon one or more of the first uplink shared channel transmission occasionidentifier, the first random access occasion identifier, a preamblesequence identifier provided in the system information, or anycombinations thereof. In some examples, the reference signal sequencemanager 1035 may determine a base sequence based on one or more of agroup index, a sequence index, a cyclic shift, or any combinationsthereof, indicated in the system information. In some cases, theinitialization seed is further based on one or more of a symbol index ofa symbol within a transmission slot that carries the reference signal, atransmission slot number of the transmission slot within a radio frame,a sub-carrier spacing used for transmitting the first random accessmessage, one or more scaling constants, or any combinations thereof. Insome cases, the reference signal sequence is a preconfigured goldsequence that is selected from a set of available preconfigured goldsequences based on the first random access occasion identifier and thefirst uplink shared channel transmission occasion identifier.

In some cases, the reference signal sequence includes a cyclic prefixorthogonal frequency division multiplexing (CP-OFDM) waveformdemodulation reference signal (DMRS) sequence.

In some cases, the group index is determined based on one or more of thefirst uplink shared channel transmission occasion identifier, the firstrandom access occasion identifier, a preamble sequence identifierprovided in the system information, or any combinations thereof. In somecases, the group index is further determined based on a group hoppingindex provided in the system information, a reference signal sequencehopping index provided in the system information, or any combinationsthereof.

In some cases, the reference signal sequence includes a discrete Fouriertransform spread orthogonal frequency division multiplexing (DFT-s-OFDM)waveform demodulation reference signal (DMRS) sequence. In some cases,the base sequence is selected from a set of available base sequencesincluding Zadoff-Chu sequences, computer generated sequences, modifiedchirp sequences, composite sequences with low peak to average powerratios, or any combinations thereof.

The RO manager 1040 may select a first random access occasion of the twoor more available random access occasions and a first uplink sharedchannel transmission occasion of the two or more available uplink sharedchannel transmission occasions for transmission of a first random accessmessage. The random access preamble manager 1030 may determine a randomaccess preamble for transmission with the first random access message.

In some examples, the communications manager 1005 may be included in aUE that is in RRC connected state. In such examples, the systeminformation manager 1010 may receive the system information via RRCsignaling. In other examples, system information manager 1010 mayreceive the system information via physical layer signaling (e.g., in aSIB message).

In some examples, the two or more available random access occasions andtwo or more available uplink shared channel transmission occasions areassociated with an RRC state. In such examples, the RO manager 1040 mayselect the first random access occasion and the first uplink sharedchannel transmission occasion based on the UE being in the RRC state.

The polynomial generator 1045 may generate a polynomial for thereference signal sequence. In some cases, the polynomial generator is aclosed-form polynomial generator that generates a pseudo-random noise(PN) sequence or other DMRS sequence.

FIG. 11 shows a diagram of a system 1100 including a device 1105 thatsupports reference signal transmission techniques for random accessmessages in accordance with aspects of the present disclosure. Thedevice 1105 may be an example of or include the components of device805, device 905, or a UE 115 as described herein. The device 1105 mayinclude components for bi-directional voice and data communicationsincluding components for transmitting and receiving communications,including a communications manager 1110, an I/O controller 1115, atransceiver 1120, an antenna 1125, memory 1130, and a processor 1140.These components may be in electronic communication via one or morebuses (e.g., bus 1145).

The communications manager 1110 may receive system information from abase station, the system information including an indication of two ormore available uplink shared channel transmission occasions for a randomaccess message transmission from the UE, select a first uplink sharedchannel transmission occasion of the two or more available uplink sharedchannel transmission occasions for transmission of a first random accessmessage, where the first uplink shared channel transmission occasionspans at least two transmission slots, determine, based on the systeminformation, reference signal resources within the first uplink sharedchannel transmission occasion for transmitting a reference signal withthe first random access message, where the reference signal resourcesinclude at least one symbol in each of the two or more transmissionslots, format the first random access message based on the selectedfirst uplink shared channel transmission occasion and the determinedreference signal resources, the first random access message includingthe reference signal and uplink shared channel data, and transmit thefirst random access message to the base station.

The communications manager 1110 may also receive system information froma base station, the system information including an indication of two ormore available random access occasions and two or more available uplinkshared channel transmission occasions within each of the two or moreavailable random access occasions, where each of the two or moreavailable random access occasions is indicated by an associated randomaccess occasion identifier and each of the two or more available uplinkshared channel transmission occasions is indicated by an associateduplink shared channel transmission occasion identifier, select a firstrandom access occasion of the two or more available random accessoccasions and a first uplink shared channel transmission occasion of thetwo or more available uplink shared channel transmission occasions fortransmission of a first random access message, determine, based on afirst random access occasion identifier associated with the first randomaccess occasion, a first uplink shared channel transmission occasionidentifier associated with the first uplink shared channel transmissionoccasion, or combinations thereof, a reference signal sequence for areference signal to be transmitted with the first random access message,and transmit the first random access message to the base station.

The I/O controller 1115 may manage input and output signals for thedevice 1105. The I/O controller 1115 may also manage peripherals notintegrated into the device 1105. In some cases, the I/O controller 1115may represent a physical connection or port to an external peripheral.In some cases, the I/O controller 1115 may utilize an operating systemsuch as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, oranother known operating system. In other cases, the I/O controller 1115may represent or interact with a modem, a keyboard, a mouse, atouchscreen, or a similar device. In some cases, the I/O controller 1115may be implemented as part of a processor. In some cases, a user mayinteract with the device 1105 via the I/O controller 1115 or viahardware components controlled by the I/O controller 1115.

The transceiver 1120 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1120 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1120 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1125.However, in some cases the device may have more than one antenna 1125,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1130 may include RAM and ROM. The memory 1130 may storecomputer-readable, computer-executable code 1135 including instructionsthat, when executed, cause the processor to perform various functionsdescribed herein. In some cases, the memory 1130 may contain, amongother things, a basic input/output system (BIOS) which may control basichardware or software operation such as the interaction with peripheralcomponents or devices.

The processor 1140 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1140 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into the processor 1140. The processor 1140 may beconfigured to execute computer-readable instructions stored in a memory(e.g., the memory 1130) to cause the device 1105 to perform variousfunctions (e.g., functions or tasks supporting reference signaltransmission techniques for random access messages).

The code 1135 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1135 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1135 may not be directly executable by theprocessor 1140 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 12 shows a block diagram 1200 of a device 1205 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. The device 1205 maybe an example of aspects of a base station 105 as described herein. Thedevice 1205 may include a receiver 1210, a communications manager 1215,and a transmitter 1220. The device 1205 may also include a processor.Each of these components may be in communication with one another (e.g.,via one or more buses).

The receiver 1210 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to referencesignal transmission techniques for random access messages, etc.).Information may be passed on to other components of the device 1205. Thereceiver 1210 may be an example of aspects of the transceiver 1520described with reference to FIG. 15. The receiver 1210 may utilize asingle antenna or a set of antennas.

The communications manager 1215 may determine two or more uplink sharedchannel transmission occasions for a random access message transmissionfrom at least a first UE of a set of UEs served by the base station,where at least a first uplink shared channel transmission occasion ofthe two or more uplink shared channel transmission occasions spans twoor more transmission slots, configure reference signal resources foreach of the two or more uplink shared channel transmission occasions,where the reference signal resources for the first uplink shared channeltransmission occasion include at least one symbol in each of the two ormore transmission slots, transmit system information to the set of UEsthat indicates the two or more uplink shared channel transmissionoccasions, and the configured reference signal resources, that areavailable for random access message transmissions of the set of UEs, andreceive a first random access message from the first UE based on areference signal transmitted in the reference signal resourcesassociated with the uplink shared channel transmission occasion selectedby the first UE for transmission of the first random access message.

The communications manager 1215 may also configure two or more randomaccess occasions and two or more uplink shared channel transmissionoccasions within each of the two or more random access occasions thatare available for at least a first UE to transmit a first random accessmessage, where each of the two or more random access occasions has anassociated random access occasion identifier and each of the two or moreuplink shared channel transmission occasions has an associated uplinkshared channel transmission occasion identifier, transmit systeminformation to a set of UEs, the system information including randomaccess occasion identifiers of the configured two or more random accessoccasions and uplink shared channel transmission occasion identifiers ofthe configured two or more uplink shared channel transmission occasions,receive the first random access message from the first UE in a firstuplink shared channel transmission occasion of a first random accessoccasions, where the first random access message includes a referencesignal, demodulate the first random access message based on thedetermined reference signal sequence, and determine, based on a firstrandom access occasion identifier associated with the first randomaccess occasion and a first uplink shared channel transmission occasionidentifier associated with the first uplink shared channel transmissionoccasion, a reference signal sequence for the reference signaltransmitted with the first random access message. The communicationsmanager 1215 may be an example of aspects of the communications manager1510 described herein.

The communications manager 1215, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the communications manager 1215, or itssub-components may be executed by a general-purpose processor, a DSP, anapplication-specific integrated circuit (ASIC), a FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The communications manager 1215, or its sub-components, may bephysically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical components. In some examples, thecommunications manager 1215, or its sub-components, may be a separateand distinct component in accordance with various aspects of the presentdisclosure. In some examples, the communications manager 1215, or itssub-components, may be combined with one or more other hardwarecomponents, including but not limited to an input/output (I/O)component, a transceiver, a network server, another computing device,one or more other components described in the present disclosure, or acombination thereof in accordance with various aspects of the presentdisclosure.

The transmitter 1220 may transmit signals generated by other componentsof the device 1205. In some examples, the transmitter 1220 may becollocated with a receiver 1210 in a transceiver module. For example,the transmitter 1220 may be an example of aspects of the transceiver1520 described with reference to FIG. 15. The transmitter 1220 mayutilize a single antenna or a set of antennas.

FIG. 13 shows a block diagram 1300 of a device 1305 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. The device 1305 maybe an example of aspects of a device 1205, or a base station 105 asdescribed herein. The device 1305 may include a receiver 1310, acommunications manager 1315, and a transmitter 1350. The device 1305 mayalso include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

The receiver 1310 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to referencesignal transmission techniques for random access messages, etc.).Information may be passed on to other components of the device 1305. Thereceiver 1310 may be an example of aspects of the transceiver 1520described with reference to FIG. 15. The receiver 1310 may utilize asingle antenna or a set of antennas.

The communications manager 1315 may be an example of aspects of thecommunications manager 1215 as described herein. The communicationsmanager 1315 may include a PO manager 1320, a reference signal resourcemanager 1325, a system information manager 1330, a random access messagemanager 1335, a RO manager 1340, and a reference signal sequence manager1345. The communications manager 1315 may be an example of aspects ofthe communications manager 1510 described herein.

The PO manager 1320 may determine two or more uplink shared channeltransmission occasions for a random access message transmission from atleast a first UE of a set of UEs served by the base station, where atleast a first uplink shared channel transmission occasion of the two ormore uplink shared channel transmission occasions spans two or moretransmission slots.

The reference signal resource manager 1325 may configure referencesignal resources for each of the two or more uplink shared channeltransmission occasions, where the reference signal resources for thefirst uplink shared channel transmission occasion include at least onesymbol in each of the two or more transmission slots.

The system information manager 1330 may transmit system information tothe set of UEs that indicates the two or more uplink shared channeltransmission occasions, and the configured reference signal resources,that are available for random access message transmissions of the set ofUEs.

The random access message manager 1335 may receive a first random accessmessage from the first UE based on a reference signal transmitted in thereference signal resources associated with the uplink shared channeltransmission occasion selected by the first UE for transmission of thefirst random access message.

The RO manager 1340 may configure two or more random access occasionsand two or more uplink shared channel transmission occasions within eachof the two or more random access occasions that are available for atleast a first UE to transmit a first random access message, where eachof the two or more random access occasions has an associated randomaccess occasion identifier and each of the two or more uplink sharedchannel transmission occasions has an associated uplink shared channeltransmission occasion identifier.

In some cases, the reference signal resource manager 1325 may transmitsystem information to a set of UEs, the system information includingrandom access occasion identifiers of the configured two or more randomaccess occasions and uplink shared channel transmission occasionidentifiers of the configured two or more uplink shared channeltransmission occasions. The random access message manager 1335 mayreceive the first random access message from the first UE in a firstuplink shared channel transmission occasion of a first random accessoccasions, where the first random access message includes a referencesignal and demodulate the first random access message based on thedetermined reference signal sequence. The reference signal sequencemanager 1345 may determine, based on a first random access occasionidentifier associated with the first random access occasion and a firstuplink shared channel transmission occasion identifier associated withthe first uplink shared channel transmission occasion, a referencesignal sequence for the reference signal transmitted with the firstrandom access message.

The transmitter 1350 may transmit signals generated by other componentsof the device 1305. In some examples, the transmitter 1350 may becollocated with a receiver 1310 in a transceiver module. For example,the transmitter 1350 may be an example of aspects of the transceiver1520 described with reference to FIG. 15. The transmitter 1350 mayutilize a single antenna or a set of antennas.

FIG. 14 shows a block diagram 1400 of a communications manager 1405 thatsupports reference signal transmission techniques for random accessmessages in accordance with aspects of the present disclosure. Thecommunications manager 1405 may be an example of aspects of acommunications manager 1215, a communications manager 1315, or acommunications manager 1510 described herein. The communications manager1405 may include a PO manager 1410, a reference signal resource manager1415, a system information manager 1420, a random access message manager1425, a random access preamble manager 1430, a reference signal sequencemanager 1435, a RO manager 1440, and a polynomial generator 1445. Eachof these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses).

The PO manager 1410 may determine two or more uplink shared channeltransmission occasions for a random access message transmission from atleast a first UE of a set of UEs served by the base station, where atleast a first uplink shared channel transmission occasion of the two ormore uplink shared channel transmission occasions spans two or moretransmission slots. In some examples, the PO manager 1410 may determinethe two or more shared uplink channel transmission occasions for a RRCstate.

The reference signal resource manager 1415 may configure referencesignal resources for each of the two or more uplink shared channeltransmission occasions, where the reference signal resources for thefirst uplink shared channel transmission occasion include at least onesymbol in each of the two or more transmission slots.

In some examples, the reference signal resource manager 1415 maytransmit system information to a set of UEs, the system informationincluding random access occasion identifiers of the configured two ormore random access occasions and uplink shared channel transmissionoccasion identifiers of the configured two or more uplink shared channeltransmission occasions. In some cases, the reference signal is ademodulation reference signal, and where the reference signal resourcesin each of the two or more transmission slots are front-loaded in eachof the at least two transmission slots, are distributed in each of theat least two transmission slots, or combinations thereof. In someexamples, the reference signal resource manager 1415 may transmit thesystem information in a SIB, in an RRC message, or both.

The system information manager 1420 may transmit system information tothe set of UEs that indicates the two or more uplink shared channeltransmission occasions, and the configured reference signal resources,that are available for random access message transmissions of the set ofUEs.

In some examples, the system information manager 1420 may configure anindication of two or more cover code codebooks in the systeminformation, and where at least a first cover code of a first cover codecodebook spans all of the reference signal resources in each of the twoor more transmission slots of the first uplink shared channeltransmission occasion. In some examples, the system information manager1420 may configure different cover code codebooks for each of the two ormore transmission slots of the first uplink shared channel transmissionoccasion.

The random access message manager 1425 may receive a first random accessmessage from the first UE based on a reference signal transmitted in thereference signal resources associated with the uplink shared channeltransmission occasion selected by the first UE for transmission of thefirst random access message.

In some examples, the random access message manager 1425 may receive thefirst random access message from the first UE in a first uplink sharedchannel transmission occasion of a first random access occasions, wherethe first random access message includes a reference signal. In someexamples, the random access message manager 1425 may demodulate thefirst random access message based on the determined reference signalsequence.

In some examples, the random access message manager 1425 may demodulateand decode a payload of the first random access message based on therandom access preamble and the reference signal sequence.

The reference signal sequence manager 1435 may determine, based on afirst random access occasion identifier associated with the first randomaccess occasion and a first uplink shared channel transmission occasionidentifier associated with the first uplink shared channel transmissionoccasion, a reference signal sequence for the reference signaltransmitted with the first random access message. In some examples, thereference signal sequence manager 1435 may determine a reference signalsequence of the reference signal of the first random access messagebased on the random access preamble of the first random access message.

In some examples, the reference signal sequence manager 1435 may decodethe first random access message based on a cover code applied to thereference signal that is associated with the first UE. In some cases,the cover code is a binary orthogonal cover code, a non-binaryorthogonal cover code, or a quasi-orthogonal cover code. In some cases,the different cover code codebooks are each associated with differentsubsets of the two or more uplink shared channel transmission occasions.In some cases, the cover codes are applied separately or jointly acrossfrequency domain resources associated with the two or more uplink sharedchannel transmission occasions.

In some examples, the reference signal sequence manager 1435 maydetermine an initialization seed for a polynomial generator thatgenerates the reference signal sequence, the initialization seed basedon one or more of the first uplink shared channel transmission occasionidentifier, the first random access occasion identifier, a preamblesequence identifier provided in the system information, or anycombinations thereof. In some examples, the reference signal sequencemanager 1435 may determine a base sequence based on one or more of agroup index, a sequence index, a cyclic shift, or any combinationsthereof, indicated in the system information. In some cases, theinitialization seed is further based on one or more of a symbol index ofa symbol within a transmission slot that carries the reference signal, atransmission slot number of the transmission slot within a radio frame,a sub-carrier spacing used for transmitting the first random accessmessage, one or more scaling constants, or any combinations thereof. Insome cases, the reference signal sequence is a preconfigured goldsequence that is selected from a set of available preconfigured goldsequences based on the first random access occasion identifier and thefirst uplink shared channel transmission occasion identifier.

In some cases, the reference signal sequence includes a cyclic prefixorthogonal frequency division multiplexing (CP-OFDM) waveformdemodulation reference signal (DMRS) sequence.

In some cases, the group index is determined based on one or more of thefirst uplink shared channel transmission occasion identifier, the firstrandom access occasion identifier, a preamble sequence identifierprovided in the system information, or any combinations thereof. In somecases, the group index is further determined based on a group hoppingindex provided in the system information, a reference signal sequencehopping index provided in the system information, or any combinationsthereof.

In some cases, the reference signal sequence includes a discrete Fouriertransform spread orthogonal frequency division multiplexing (DFT-s-OFDM)waveform demodulation reference signal (DMRS) sequence. In some cases,the base sequence is selected from a set of available base sequencesincluding Zadoff-Chu sequences, computer generated sequences, modifiedchirp sequences, composite sequences with low peak to average powerratios, or any combinations thereof.

The RO manager 1440 may configure two or more random access occasionsand two or more uplink shared channel transmission occasions within eachof the two or more random access occasions that are available for atleast a first UE to transmit a first random access message, where eachof the two or more random access occasions has an associated randomaccess occasion identifier and each of the two or more uplink sharedchannel transmission occasions has an associated uplink shared channeltransmission occasion identifier.

The random access preamble manager 1430 may determine a random accesspreamble of the first random access message.

The polynomial generator 1445 may generate a polynomial that is used todetermine a DMRS sequence. In some cases, the polynomial generator is aclosed-form polynomial generator that generates a pseudo-random noise(PN) sequence.

FIG. 15 shows a diagram of a system 1500 including a device 1505 thatsupports reference signal transmission techniques for random accessmessages in accordance with aspects of the present disclosure. Thedevice 1505 may be an example of or include the components of device1205, device 1305, or a base station 105 as described herein. The device1505 may include components for bi-directional voice and datacommunications including components for transmitting and receivingcommunications, including a communications manager 1510, a networkcommunications manager 1515, a transceiver 1520, an antenna 1525, memory1530, a processor 1540, and an inter-station communications manager1545. These components may be in electronic communication via one ormore buses (e.g., bus 1550).

The communications manager 1510 may determine two or more uplink sharedchannel transmission occasions for a random access message transmissionfrom at least a first UE of a set of UEs served by the base station,where at least a first uplink shared channel transmission occasion ofthe two or more uplink shared channel transmission occasions spans twoor more transmission slots, configure reference signal resources foreach of the two or more uplink shared channel transmission occasions,where the reference signal resources for the first uplink shared channeltransmission occasion include at least one symbol in each of the two ormore transmission slots, transmit system information to the set of UEsthat indicates the two or more uplink shared channel transmissionoccasions, and the configured reference signal resources, that areavailable for random access message transmissions of the set of UEs, andreceive a first random access message from the first UE based on areference signal transmitted in the reference signal resourcesassociated with the uplink shared channel transmission occasion selectedby the first UE for transmission of the first random access message.

The communications manager 1510 may also configure two or more randomaccess occasions and two or more uplink shared channel transmissionoccasions within each of the two or more random access occasions thatare available for at least a first UE to transmit a first random accessmessage, where each of the two or more random access occasions has anassociated random access occasion identifier and each of the two or moreuplink shared channel transmission occasions has an associated uplinkshared channel transmission occasion identifier, transmit systeminformation to a set of UEs, the system information including randomaccess occasion identifiers of the configured two or more random accessoccasions and uplink shared channel transmission occasion identifiers ofthe configured two or more uplink shared channel transmission occasions,receive the first random access message from the first UE in a firstuplink shared channel transmission occasion of a first random accessoccasions, where the first random access message includes a referencesignal, demodulate the first random access message based on thedetermined reference signal sequence, and determine, based on a firstrandom access occasion identifier associated with the first randomaccess occasion and a first uplink shared channel transmission occasionidentifier associated with the first uplink shared channel transmissionoccasion, a reference signal sequence for the reference signaltransmitted with the first random access message.

The network communications manager 1515 may manage communications withthe core network (e.g., via one or more wired backhaul links). Forexample, the network communications manager 1515 may manage the transferof data communications for client devices, such as one or more UEs 115.

The transceiver 1520 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1520 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1520 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1525.However, in some cases the device may have more than one antenna 1525,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1530 may include RAM, ROM, or a combination thereof. Thememory 1530 may store computer-readable code 1535 including instructionsthat, when executed by a processor (e.g., the processor 1540) cause thedevice to perform various functions described herein. In some cases, thememory 1530 may contain, among other things, a BIOS which may controlbasic hardware or software operation such as the interaction withperipheral components or devices.

The processor 1540 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1540 may be configured to operate a memoryarray using a memory controller. In some cases, a memory controller maybe integrated into processor 1540. The processor 1540 may be configuredto execute computer-readable instructions stored in a memory (e.g., thememory 1530) to cause the device 1505 to perform various functions(e.g., functions or tasks supporting reference signal transmissiontechniques for random access messages).

The inter-station communications manager 1545 may manage communicationswith other base station 105, and may include a controller or schedulerfor controlling communications with UEs 115 in cooperation with otherbase stations 105. For example, the inter-station communications manager1545 may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, the inter-station communications manager1545 may provide an X2 interface within an LTE/LTE-A wirelesscommunication network technology to provide communication between basestations 105.

The code 1535 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1535 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1535 may not be directly executable by theprocessor 1540 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 16 shows a flowchart illustrating a method 1600 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. The operations ofmethod 1600 may be implemented by a UE 115 or its components asdescribed herein. For example, the operations of method 1600 may beperformed by a communications manager as described with reference toFIGS. 8 through 11. In some examples, a UE may execute a set ofinstructions to control the functional elements of the UE to perform thefunctions described below. Additionally or alternatively, a UE mayperform aspects of the functions described below using special-purposehardware.

At 1605, the UE may receive system information from a base station, thesystem information including an indication of two or more availableuplink shared channel transmission occasions for a random access messagetransmission from the UE. The operations of 1605 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1605 may be performed by a system information manageras described with reference to FIGS. 8 through 11.

At 1610, the UE may select a first uplink shared channel transmissionoccasion of the two or more available uplink shared channel transmissionoccasions for transmission of a first random access message, where thefirst uplink shared channel transmission occasion spans at least twotransmission slots. The operations of 1610 may be performed according tothe methods described herein. In some examples, aspects of theoperations of 1610 may be performed by a PO manager as described withreference to FIGS. 8 through 11.

At 1615, the UE may determine, based on the system information,reference signal resources within the first uplink shared channeltransmission occasion for transmitting a reference signal with the firstrandom access message, where the reference signal resources include atleast one symbol in each of the two or more transmission slots. Theoperations of 1615 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1615 may beperformed by a reference signal resource manager as described withreference to FIGS. 8 through 11.

At 1620, the UE may format the first random access message based on theselected first uplink shared channel transmission occasion and thedetermined reference signal resources, the first random access messageincluding the reference signal and uplink shared channel data. Theoperations of 1620 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1620 may beperformed by a random access message manager as described with referenceto FIGS. 8 through 11.

At 1625, the UE may transmit the first random access message to the basestation. The operations of 1625 may be performed according to themethods described herein. In some examples, aspects of the operations of1625 may be performed by a random access message manager as describedwith reference to FIGS. 8 through 11.

FIG. 17 shows a flowchart illustrating a method 1700 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. The operations ofmethod 1700 may be implemented by a UE 115 or its components asdescribed herein. For example, the operations of method 1700 may beperformed by a communications manager as described with reference toFIGS. 8 through 11. In some examples, a UE may execute a set ofinstructions to control the functional elements of the UE to perform thefunctions described below. Additionally or alternatively, a UE mayperform aspects of the functions described below using special-purposehardware.

At 1705, the UE may receive system information from a base station, thesystem information including an indication of two or more availableuplink shared channel transmission occasions for a random access messagetransmission from the UE. The operations of 1705 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1705 may be performed by a system information manageras described with reference to FIGS. 8 through 11.

At 1710, the UE may select a first uplink shared channel transmissionoccasion of the two or more available uplink shared channel transmissionoccasions for transmission of a first random access message, where thefirst uplink shared channel transmission occasion spans at least twotransmission slots. The operations of 1710 may be performed according tothe methods described herein. In some examples, aspects of theoperations of 1710 may be performed by a PO manager as described withreference to FIGS. 8 through 11.

At 1715, the UE may determine, based on the system information,reference signal resources within the first uplink shared channeltransmission occasion for transmitting a reference signal with the firstrandom access message, where the reference signal resources include atleast one symbol in each of the two or more transmission slots. Theoperations of 1715 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1715 may beperformed by a reference signal resource manager as described withreference to FIGS. 8 through 11.

At 1720, the UE may determine a random access preamble for transmissionwith the first random access message. The operations of 1720 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1720 may be performed by a random accesspreamble manager as described with reference to FIGS. 8 through 11.

At 1725, the UE may determine a reference signal sequence for thereference signal based on the random access preamble. The operations of1725 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1725 may be performed by areference signal sequence manager as described with reference to FIGS. 8through 11.

At 1730, the UE may apply a cover code to the reference signal that isassociated with the UE. The operations of 1730 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1730 may be performed by a reference signal sequencemanager as described with reference to FIGS. 8 through 11.

At 1735, the UE may format the first random access message based on theselected first uplink shared channel transmission occasion and thedetermined reference signal resources, the first random access messageincluding the reference signal and uplink shared channel data. Theoperations of 1735 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1735 may beperformed by a random access message manager as described with referenceto FIGS. 8 through 11.

At 1740, the UE may transmit the first random access message to the basestation. The operations of 1740 may be performed according to themethods described herein. In some examples, aspects of the operations of1740 may be performed by a random access message manager as describedwith reference to FIGS. 8 through 11.

FIG. 18 shows a flowchart illustrating a method 1800 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. The operations ofmethod 1800 may be implemented by a UE 115 or its components asdescribed herein. For example, the operations of method 1800 may beperformed by a communications manager as described with reference toFIGS. 8 through 11. In some examples, a UE may execute a set ofinstructions to control the functional elements of the UE to perform thefunctions described below. Additionally or alternatively, a UE mayperform aspects of the functions described below using special-purposehardware.

At 1805, the UE may receive system information from a base station, thesystem information including an indication of two or more availablerandom access occasions and two or more available uplink shared channeltransmission occasions within each of the two or more available randomaccess occasions, where each of the two or more available random accessoccasions is indicated by an associated random access occasionidentifier and each of the two or more available uplink shared channeltransmission occasions is indicated by an associated uplink sharedchannel transmission occasion identifier. The operations of 1805 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1805 may be performed by a systeminformation manager as described with reference to FIGS. 8 through 11.

At 1810, the UE may select a first random access occasion of the two ormore available random access occasions and a first uplink shared channeltransmission occasion of the two or more available uplink shared channeltransmission occasions for transmission of a first random accessmessage. The operations of 1810 may be performed according to themethods described herein. In some examples, aspects of the operations of1810 may be performed by a RO manager as described with reference toFIGS. 8 through 11.

At 1815, the UE may determine, based on a first random access occasionidentifier associated with the first random access occasion, a firstuplink shared channel transmission occasion identifier associated withthe first uplink shared channel transmission occasion, or combinationsthereof, a reference signal sequence for a reference signal to betransmitted with the first random access message. The operations of 1815may be performed according to the methods described herein. In someexamples, aspects of the operations of 1815 may be performed by areference signal sequence manager as described with reference to FIGS. 8through 11.

At 1820, the UE may transmit the first random access message to the basestation. The operations of 1820 may be performed according to themethods described herein. In some examples, aspects of the operations of1820 may be performed by a random access message manager as describedwith reference to FIGS. 8 through 11.

FIG. 19 shows a flowchart illustrating a method 1900 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. The operations ofmethod 1900 may be implemented by a UE 115 or its components asdescribed herein. For example, the operations of method 1900 may beperformed by a communications manager as described with reference toFIGS. 8 through 11. In some examples, a UE may execute a set ofinstructions to control the functional elements of the UE to perform thefunctions described below. Additionally or alternatively, a UE mayperform aspects of the functions described below using special-purposehardware.

At 1905, the UE may receive system information from a base station, thesystem information including an indication of two or more availablerandom access occasions and two or more available uplink shared channeltransmission occasions within each of the two or more available randomaccess occasions, where each of the two or more available random accessoccasions is indicated by an associated random access occasionidentifier and each of the two or more available uplink shared channeltransmission occasions is indicated by an associated uplink sharedchannel transmission occasion identifier. The operations of 1905 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1905 may be performed by a systeminformation manager as described with reference to FIGS. 8 through 11.

At 1910, the UE may select a first random access occasion of the two ormore available random access occasions and a first uplink shared channeltransmission occasion of the two or more available uplink shared channeltransmission occasions for transmission of a first random accessmessage. The operations of 1910 may be performed according to themethods described herein. In some examples, aspects of the operations of1910 may be performed by a RO manager as described with reference toFIGS. 8 through 11.

At 1915, the UE may determine, based on a first random access occasionidentifier associated with the first random access occasion, a firstuplink shared channel transmission occasion identifier associated withthe first uplink shared channel transmission occasion, or combinationsthereof, a reference signal sequence for a reference signal to betransmitted with the first random access message. The operations of 1915may be performed according to the methods described herein. In someexamples, aspects of the operations of 1915 may be performed by areference signal sequence manager as described with reference to FIGS. 8through 11.

At 1920, the UE may determine an initialization seed for a polynomialgenerator that generates the reference signal sequence, theinitialization seed based on one or more of the first uplink sharedchannel transmission occasion identifier, the first random accessoccasion identifier, a preamble sequence identifier provided in thesystem information, or any combinations thereof. The operations of 1920may be performed according to the methods described herein. In someexamples, aspects of the operations of 1920 may be performed by areference signal sequence manager as described with reference to FIGS. 8through 11.

At 1925, the UE may transmit the first random access message to the basestation. The operations of 1925 may be performed according to themethods described herein. In some examples, aspects of the operations of1925 may be performed by a random access message manager as describedwith reference to FIGS. 8 through 11.

FIG. 20 shows a flowchart illustrating a method 2000 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. The operations ofmethod 2000 may be implemented by a base station 105 or its componentsas described herein. For example, the operations of method 2000 may beperformed by a communications manager as described with reference toFIGS. 12 through 15. In some examples, a base station may execute a setof instructions to control the functional elements of the base stationto perform the functions described below. Additionally or alternatively,a base station may perform aspects of the functions described belowusing special-purpose hardware.

At 2005, the base station may determine two or more uplink sharedchannel transmission occasions for a random access message transmissionfrom at least a first UE of a set of UEs served by the base station,where at least a first uplink shared channel transmission occasion ofthe two or more uplink shared channel transmission occasions spans twoor more transmission slots. The operations of 2005 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 2005 may be performed by a PO manager as describedwith reference to FIGS. 12 through 15.

At 2010, the base station may configure reference signal resources foreach of the two or more uplink shared channel transmission occasions,where the reference signal resources for the first uplink shared channeltransmission occasion include at least one symbol in each of the two ormore transmission slots. The operations of 2010 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 2010 may be performed by a reference signal resourcemanager as described with reference to FIGS. 12 through 15.

At 2015, the base station may transmit system information to the set ofUEs that indicates the two or more uplink shared channel transmissionoccasions, and the configured reference signal resources, that areavailable for random access message transmissions of the set of UEs. Theoperations of 2015 may be performed according to the methods describedherein. In some examples, aspects of the operations of 2015 may beperformed by a system information manager as described with reference toFIGS. 12 through 15.

At 2020, the base station may receive a first random access message fromthe first UE based on a reference signal transmitted in the referencesignal resources associated with the uplink shared channel transmissionoccasion selected by the first UE for transmission of the first randomaccess message. The operations of 2020 may be performed according to themethods described herein. In some examples, aspects of the operations of2020 may be performed by a random access message manager as describedwith reference to FIGS. 12 through 15.

FIG. 21 shows a flowchart illustrating a method 2100 that supportsreference signal transmission techniques for random access messages inaccordance with aspects of the present disclosure. The operations ofmethod 2100 may be implemented by a base station 105 or its componentsas described herein. For example, the operations of method 2100 may beperformed by a communications manager as described with reference toFIGS. 12 through 15. In some examples, a base station may execute a setof instructions to control the functional elements of the base stationto perform the functions described below. Additionally or alternatively,a base station may perform aspects of the functions described belowusing special-purpose hardware.

At 2105, the base station may configure two or more random accessoccasions and two or more uplink shared channel transmission occasionswithin each of the two or more random access occasions that areavailable for at least a first UE to transmit a first random accessmessage, where each of the two or more random access occasions has anassociated random access occasion identifier and each of the two or moreuplink shared channel transmission occasions has an associated uplinkshared channel transmission occasion identifier. The operations of 2105may be performed according to the methods described herein. In someexamples, aspects of the operations of 2105 may be performed by a ROmanager as described with reference to FIGS. 12 through 15.

At 2110, the base station may transmit system information to a set ofUEs, the system information including random access occasion identifiersof the configured two or more random access occasions and uplink sharedchannel transmission occasion identifiers of the configured two or moreuplink shared channel transmission occasions. The operations of 2110 maybe performed according to the methods described herein. In someexamples, aspects of the operations of 2110 may be performed by areference signal resource manager as described with reference to FIGS.12 through 15.

At 2115, the base station may receive the first random access messagefrom the first UE in a first uplink shared channel transmission occasionof a first random access occasions, where the first random accessmessage includes a reference signal. The operations of 2115 may beperformed according to the methods described herein. In some examples,aspects of the operations of 2115 may be performed by a random accessmessage manager as described with reference to FIGS. 12 through 15.

At 2120, the base station may determine, based on a first random accessoccasion identifier associated with the first random access occasion anda first uplink shared channel transmission occasion identifierassociated with the first uplink shared channel transmission occasion, areference signal sequence for the reference signal transmitted with thefirst random access message. The operations of 2120 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 2120 may be performed by a reference signal sequencemanager as described with reference to FIGS. 12 through 15.

At 2125, the base station may demodulate the first random access messagebased on the determined reference signal sequence. The operations of2125 may be performed according to the methods described herein. In someexamples, aspects of the operations of 2125 may be performed by a randomaccess message manager as described with reference to FIGS. 12 through15.

It should be noted that the methods described herein describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.A CDMA system may implement a radio technology such as CDMA2000,Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,IS-95, and IS-856 standards. IS-2000 Releases may be commonly referredto as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as Global System for MobileCommunications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releasesof UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR,and GSM are described in documents from the organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned herein as well as other systemsand radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NRsystem may be described for purposes of example, and LTE, LTE-A, LTE-APro, or NR terminology may be used in much of the description, thetechniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro,or NR applications.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell maybe associated with a lower-powered base station, as compared with amacro cell, and a small cell may operate in the same or different (e.g.,licensed, unlicensed, etc.) frequency bands as macro cells. Small cellsmay include pico cells, femto cells, and micro cells according tovarious examples. A pico cell, for example, may cover a small geographicarea and may allow unrestricted access by UEs with service subscriptionswith the network provider. A femto cell may also cover a smallgeographic area (e.g., a home) and may provide restricted access by UEshaving an association with the femto cell (e.g., UEs in a closedsubscriber group (CSG), UEs for users in the home, and the like). An eNBfor a macro cell may be referred to as a macro eNB. An eNB for a smallcell may be referred to as a small cell eNB, a pico eNB, a femto eNB, ora home eNB. An eNB may support one or multiple (e.g., two, three, four,and the like) cells, and may also support communications using one ormultiple component carriers.

The wireless communications systems described herein may supportsynchronous or asynchronous operation. For synchronous operation, thebase stations may have similar frame timing, and transmissions fromdifferent base stations may be approximately aligned in time. Forasynchronous operation, the base stations may have different frametiming, and transmissions from different base stations may not bealigned in time. The techniques described herein may be used for eithersynchronous or asynchronous operations.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA, or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices(e.g., a combination of a DSP and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROMor other optical disk storage, magnetic disk storage or other magneticstorage devices, or any other non-transitory medium that can be used tocarry or store desired program code means in the form of instructions ordata structures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, include CD, laser disc, optical disc,digital versatile disc (DVD), floppy disk and Blu-ray disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above are also includedwithin the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary step that is described as “based on conditionA” may be based on both a condition A and a condition B withoutdeparting from the scope of the present disclosure. In other words, asused herein, the phrase “based on” shall be construed in the same manneras the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication at a userequipment (UE), comprising: receiving system information from a basestation, the system information including an indication of two or moreavailable uplink shared channel transmission occasions for a randomaccess message transmission from the UE; selecting a first uplink sharedchannel transmission occasion of the two or more available uplink sharedchannel transmission occasions for transmission of a first random accessmessage, wherein the first uplink shared channel transmission occasionspans at least two transmission slots; determining, based at least inpart on the system information and the first uplink shared channeltransmission occasion, reference signal resources within the firstuplink shared channel transmission occasion for transmitting a referencesignal with the first random access message, wherein the referencesignal resources are associated with the first uplink shared channeltransmission occasion and include at least one symbol in each of the atleast two transmission slots; formatting the first random access messagebased at least in part on the selected first uplink shared channeltransmission occasion and the determined reference signal resources, thefirst random access message including the reference signal and uplinkshared channel data; and transmitting the first random access message tothe base station.
 2. The method of claim 1, further comprising:determining a random access preamble for transmission with the firstrandom access message; and determining a reference signal sequence forthe reference signal based at least in part on the random accesspreamble.
 3. The method of claim 2, wherein the reference signal is ademodulation reference signal, and wherein the reference signalresources in each of the two or more transmission slots are front-loadedin each of the at least two transmission slots, are distributed in eachof the at least two transmission slots, or combinations thereof.
 4. Themethod of claim 1, wherein the formatting further comprises: applying acover code to the reference signal that is associated with the UE. 5.The method of claim 4, wherein the formatting further comprises:determining the cover code based at least in part on a codebookindicated by the system information, and wherein the cover code spansall of the reference signal resources in each of the at least twotransmission slots.
 6. The method of claim 4, wherein the formattingfurther comprises: determining separate cover codes associated with eachof the at least two transmission slots based at least in part ondifferent codebooks associated with each of the at least twotransmission slots.
 7. The method of claim 6, wherein the differentcodebooks are each associated with different subsets of the two or moreavailable uplink shared channel transmission occasions.
 8. The method ofclaim 4, wherein the cover code is applied separately or jointly acrossfrequency domain resources associated with the two or more availableuplink shared channel transmission occasions.
 9. The method of claim 1,wherein the UE is in a radio resource control (RRC) connected state andthe system information is received via RRC signaling.